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                                                                    EXHIBIT 4.82

                                                                  CONFORMED COPY
                                                             ENGLISH TRANSLATION

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                           PLEDGE OF SHARES AGREEMENT

                                     Among :

                           MARCONI COMMUNICATIONS INC.
                      MARCONI COMMUNICATIONS, S.A. DE C.V.
                         MARCONI NETWORKS WORLDWIDE, INC
                                 the "Pledgors"

                                       and

                   THE LAW DEBENTURE TRUST CORPORATION p.l.c.
                             the "Security Trustee"

                            Dated as of May 19, 2003.

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PLEDGE OF SHARES AGREEMENT (the "Pledge of Shares Agreement") dated as of May
19, 2003, executed by and among:

         (1)      MARCONI COMMUNICATIONS INC., a corporation organized and
                  existing under the laws of the State of Delaware, United
                  States of America (hereinafter "Marconi-US");

         (2)      MARCONI COMMUNICATIONS, S.A. DE C.V., a corporation organized
                  and existing under the laws of Mexico (hereinafter
                  "Marconi-Mex");

         (3)      MARCONI NETWORKS WORLDWIDE, INC., a corporation organized and
                  existing under the laws of the State of Delaware, United
                  States of America (hereinafter "Marconi-Networks" and
                  Marconi-US, Marconi-Mex and Marconi-Networks, collectively
                  called the "Pledgors" and individually a "Pledgor");

         (4)      THE LAW DEBENTURE TRUST CORPORATION p.l.c., a corporation
                  organized and existing under the laws of England and Wales
                  with domicile at Fifth Floor, 100 Wood Street, London EC2V
                  7EX, England in its capacity as attorney-in-fact and agent for
                  the Secured Creditors (as such term is defined in the
                  Intercreditor Agreement referred to hereinbelow), its
                  successors and assigns (in each such capacity, hereinafter
                  called the "Security Trustee").

                             PRELIMINARY STATEMENTS

         I. For purposes of this Agreement, unless otherwise defined in this
Pledge of Shares Agreement, words and expressions shall have the same meanings
as attributed to them under the Intercreditor Agreement referred to hereinbelow
and the following terms shall have the following meanings:

                  (a) "Administrativa Marconi Shares" has the meaning assigned
to such term in Declaration II (a) (i) of this Pledge of Shares Agreement.

                  (b) "Enforcement Event" means the acceleration of any
Obligations, or any declaration that any Obligations are prematurely due and
payable (other than solely as a result of its becoming unlawful for a Secured
Creditor to perform its obligations under the Relevant Documents) or any failure
by any Obligor to pay any principal amount in respect of any Obligations,
whether on maturity or otherwise.

                  (c) "Intercreditor Agreement" means the security trust and
intercreditor deed dated on or about the date hereof, made among, (i) Marconi
Corporation PLC in its capacity as issuer of the Senior Notes and the Junior

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Notes (as such terms are therein defined) (the "Issuer"); (ii) The Law Debenture
Trust Corporation p.l.c., in its capacity as "Security Trustee"; (iii) the
persons therein designated as "Guarantors" and which are listed in Schedule 1 to
such Intercreditor Agreement (which together with any person who later accedes
in such capacity, are designated therein as the "Guarantors"); (iv) Law
Debenture Trust Company of New York, as senior note trustee (the "Senior Note
Trustee"); (v) JPMorgan Chase Bank as junior note trustee (the "Junior Note
Trustee"); (vi) HSBC Bank PLC as security trustee and agent under a certain New
Bonding Facility Agreement (the "New Bonding Facility Agent"); (vii) The Bank of
New York acting as depositary, paying agent and registrar (in such capacity, the
"Depositary", the "Paying Agent" and the "Registrar"); (viii) the persons
therein designated as "Intra-Group Creditors", and which are listed in Part "A"
of Schedule 2 to such Intercreditor Agreement (which together with any person
who later accedes in such capacity, are designated therein as the "Intra-Group
Creditors"); (ix) the persons therein designated as "Intra-Group Borrowers" and
which are listed in Part "B" of Schedule 2 to such Intercreditor Agreement (and
which together with any person who later accedes in such capacity, are
designated in the Intercreditor Agreement as the "Intra-Group Borrowers"); (x)
and the persons therein designated as "New Bonding Facility Banks" and which are
listed in Schedule 3 to such Intercreditor Agreement (and which together with
any person that later accedes in such capacity are designated in the
Intercreditor Agreement as the "New Bonding Facility Banks"), as it may be
further amended, varied, supplemented, or substituted from time to time,
pursuant to which the parties thereto have established the terms to regulate the
claims of the Secured Creditors (as such term is used in the Intercreditor
Agreement) and the Intra-Group Creditors against the Obligors (as such term is
used in the Intercreditor Agreement) under the Relevant Documents (as such term
is used in the Intercreditor Agreement) and the Intra-Group Liabilities (as such
term is used in the Intercreditor Agreement), and the rights of priority and
enforcement of the Secured Creditors in respect of the Security Documents (as
such term is also defined in the Intercreditor Agreement).

                  (d) "Marconi-Com-Mexico Shares" has the meaning assigned to
such term in Declaration II (a) (ii) of this Pledge of Shares Agreement.

                  (e) "Marconi Exportel Shares" has the meaning assigned to such
term in Declaration II (a) (iii) of this Pledge of Shares Agreement.

                  (f) "Marconi-Mex Shares" has the meaning assigned to such term
in Declaration I (a) of this Pledge of Shares Agreement.

                  (g) "Marconi-Mex Subsidiaries Shares" has the meaning assigned
to such term in Declaration II (a) of this Pledge of Shares Agreement.

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                  (h) "Marconi-Networks Mexican Subsidiaries Shares" has the
meaning assigned to such term in Declaration III (a) of this Pledge of Shares
Agreement.

                  (i) "Obligations" shall have the meaning given to the term
"Secured Obligations" in the Intercreditor Agreement.

                  (j) "Pledged Shares" has the meaning assigned to such term in
Declaration III (a) of this Pledge of Shares Agreement.

                  (k) "Relevant Documents" has the meaning assigned to such term
in the Intercreditor Agreement, which includes the Intercreditor Agreement, any
Agent/Trustee/New Bonding Facility Bank Accession Letter, any Guarantor
Accession Letter, the Indentures, the Escrow Agreement, the Notes, the New
Bonding Facility Agreement, the Security Documents, the Fee Letter and any
Additional Remuneration Fee Letter, and any notices issued and any other
documents or agreements entered into in connection with or relating to such
documents, and for the avoidance of any doubt, reference to any Relevant
Documents shall be to such documents as the same may be or have been from time
to time varied, amended, modified or supplemented (however fundamentally).

                  (l) "Replacement Share Certificates" has the meaning assigned
to such term in Declaration I (c) of this Pledge of Shares Agreement.

                  (m) "Secured Creditors" has the meaning set forth in the
Intercreditor Agreement, and which includes the Security Trustee, any Receiver
or Delegate, the Depositary, the Paying Agent, the Registrar, the Escrow Bank,
the Senior Note Trustee, the Junior Note Trustee and the New Bonding Facility
Agent, in their respective capacities, the holders of the Senior Notes, the
holders of the Junior Notes and each of the New Bonding Facility Banks in the
order of preference set forth in the Intercreditor Agreement and the Relevant
Documents, and Secured Creditor shall be construed accordingly.

                  (n) "Secured Obligations" means all present and future
indebtedness, liabilities and obligations (for the avoidance of doubt, including
any liabilities and obligations which have been cash-collateralized by the
Pledgors herein as Obligors), at any time of the relevant Pledgor under the
Relevant Documents, both actual and contingent and whether incurred solely or
jointly or in any other capacity together with any of the following matters
relating to or arising in respect of those liabilities and obligations: (i) any
refinancing, novation, deferral or extension; (ii) any obligation relating to
any increase in the amount of such obligations; (iii) any claim for damages or
restitution; and (iv) any claim as a result of any recovery by the Pledgor of a
payment or discharge, or non-allowability, on the grounds of preference; and any
amounts that would be

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included in any of the above but for any discharge, non-provability or
unenforceability of those amounts in any insolvency or other proceedings
(including interest accruing after the commencement of any insolvency or other
proceedings, if permitted by applicable law), including, (1) the actual,
contingent, present and/or future obligations and liabilities of the relevant
Pledgor acting as Obligor to any of the Secured Creditors under or pursuant to
the Relevant Documents, including without limitation, any and all moneys which
are or at any time shall have become due or owing by the relevant Pledgor to any
or all Secured Creditors pursuant to the Intercreditor Agreement, the
Indentures, the Notes or any of the other Relevant Documents; (2) any foreign
judgment rendered against a Pledgor in relation to any of the Relevant
Documents, that may be issued in favor of one or more of the Secured Creditors;
and (3) any of the Pledgor's obligations as Guarantor pursuant to the Guarantees
(as such term is used in the Intercreditor Agreement) and under this Pledge of
Shares Agreement.

                  (o) "Shares Missing" has the meaning assigned to such term in
Declaration I (c) of this Pledge of Shares Agreement.

                  (p) "Shares Replacement Procedure" has the meaning assigned to
such term in Declaration I (c) of this Pledge of Shares Agreement.

         II. In terms of the Indentures, the Issuer has issued or is to issue
the following debt instruments:

                  (i)      The Guaranteed Senior Secured Notes due 2008 in the
aggregate principal amount of US$717,139,584.00 (Seven Hundred and Seventeen
Million One Hundred and Thirty Nine Thousand Five Hundred and Eighty Four US
Dollars) (the "Senior Notes"), issued or to be issued by the Issuer, pursuant to
the terms of the Senior Note Indenture; and

                  (ii)     The Guaranteed Junior Secured Notes due 2008 in an
aggregate principal amount of US$486,881,472.00 (Four Hundred and Eighty Six
Million Eight Hundred and Eighty One Thousand Four Hundred and Seventy Two US
Dollars) plus any Junior PIK Notes (the "Junior Notes"), issued or to be issued
by the Issuer pursuant to the terms of the Junior Note Indenture.

         (Each of the Senior Notes and the Junior Notes shall be designated
collectively as the "Notes" and the Senior Note Indenture and the Junior Note
Indenture, shall be designated collectively as the "Indentures").

         III.     In terms of the New Bonding Facility Agreement, a committed
revolving bonding facility has been entered into among the New Bonding Facility
Agent, the New Bonding Facility Banks, the Issuer, Marconi Bonding Limited and
other members of the Group specified therein, for an amount of up to

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L50,000,000 (Fifty Million Pounds) lawful currency of the United Kingdom (or the
equivalent in other currencies), for the issuance of bonds, guarantees, letters
of credit, indemnities and similar instruments.

         IV.      In terms of Clause 6.6 of the Intercreditor Agreement, The Law
Debenture Trust Corporation p.l.c., was authorized to act on behalf of the
Secured Creditors, as agent and attorney-in-fact, for the purposes therein
described, including but not limited to, acting on behalf of the Secured
Creditors as pledgees under this Pledge of Shares Agreement.

                                  DECLARATIONS

I.- Marconi-US declares that:

         (a) As of the date hereof, it has good title to, and is the sole
beneficial and record owner of 999 (nine hundred and ninety-nine) common shares
of the capital stock of Marconi-Mex (the "Marconi-Mex Shares"), representing in
the aggregate ninety nine point ninety nine percent (99.99%) of the total
capital stock of Marconi-Mex, as contained in the share certificates listed in
Annex "A" hereto, under the name "Marconi-US Mexican Subsidiary", and which
shares will be fully paid when pledged in terms of Clause First (a) hereunder.

         (b) Except for the pledge to be created in terms hereof, the Marconi
Mex Shares are free from any Security.

         (c) Share certificates numbers 1 (one) , evidencing 650 (six hundred
and fifty) Marconi-Mex Shares, and 2 (two) evidencing 349 (three hundred and
forty nine) Marconi-Mex Shares (collectively called the "Shares Missing"), have
been misplaced and need to be reissued (the "Replacement Shares Certificates")
by Marconi-Mex based on a proper court order, after a shares replacement
procedure (the "Shares Replacement Procedure") is properly brought and
diligently prosecuted by Marconi-US before the competent courts sitting in the
jurisdiction of Marconi-Mex, and absent any opposition or other unforeseeable
events or events not in the control of Marconi-US, such Shares Replacement
Procedure has been properly concluded and only when such Replacement Share
Certificates have been duly issued, will Marconi-US be able to pledge and create
a valid and perfected security interest over the Shares Missing, albeit
Marconi-US currently appears as the owner of record of the Shares Missing in the
Shareholders Registry Book of Marconi-Mex.

II.- Marconi-Mex declares that:

         (a) As of the date hereof, it has good title to, and is the sole
beneficial and record owner of:

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                  (i)      7,743,815 (seven million seven hundred and forty
three thousand eight hundred and fifteen) fully paid common shares (the
"Administrativa Marconi Shares") of the capital stock of Administrativa Marconi
Communications S.A. de C.V. ("Administrativa Marconi") representing in the
aggregate ninety nine point ninety nine percent (99.99%) of the total capital
stock of Administrativa Marconi, and evidenced by share certificate(s) listed in
Annex "A" hereto under the name "Marconi-Mex Subsidiaries";

                  (ii)     440,724,995 (four hundred and forty million seven
hundred and twenty four thousand, nine hundred and ninety five) fully paid
common shares (the "Marconi-Com-Mexico Shares") of the capital stock of Marconi
Communications de Mexico, S.A. de C.V. ("Marconi-Com-Mexico") representing in
the aggregate ninety nine point ninety nine percent (99.99%) of the total
capital stock of Marconi-Com-Mexico, and evidenced by share certificates listed
in Annex "A" hereto under the name "Marconi-Mex Subsidiaries"; and

                  (iii)    65,999 (sixty five thousand nine hundred and
ninety-nine) fully paid common shares (the "Marconi Exportel Shares") of the
capital stock of Marconi Communications Exportel, S.A. de C.V. ("Marconi
Exportel") representing in the aggregate ninety nine point ninety nine percent
(99.99%) of the total capital stock of Marconi Exportel, and evidenced by share
certificates listed in Annex "A" hereto under the name "Marconi-Mex
Subsidiaries".

         (The Administrativa Marconi Shares, the Marconi-Com-Mexico Shares and
the Marconi Exportel Shares owned by Marconi-Mex and described in subparagraphs
(i) to (iii) before, shall be hereinafter designated collectively, as the
"Marconi-Mex Subsidiaries Shares").

         (b) Except for the pledge to be created in terms hereof, the
Marconi-Mex Subsidiaries Shares are free from any Security.

III.- Marconi-Networks declares that:

         (a) As of the date hereof, it has good title to, and is the sole
beneficial and record owner of:

                  (i)      1 (one) fully paid common share of the capital stock
of Marconi-Mex representing in the aggregate point zero one percent (.01%) of
the total capital stock of Marconi-Mex, and evidenced by share certificate
listed in Annex "A" hereto under the name "Marconi-Networks Mexican Subsidiaries
Shares";

                  (ii)     1 (one) fully paid common share of the capital stock
of Administrativa-Marconi representing in the aggregate point zero one percent
(.01%) of the total capital stock of Administrativa-Marconi, and evidenced by

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share certificate listed in Annex "A" hereto under the name "Marconi-Networks
Mexican Subsidiaries Shares";

                  (iii)    1 (one) fully paid common share of the capital stock
of Marconi-Com-Mexico representing in the aggregate point zero one percent
(.01%) of the total capital stock of Marconi-Com-Mexico, and evidenced by share
certificate listed in Annex "A" hereto under the name "Marconi-Networks Mexican
Subsidiaries Shares"; and

                  (iv)     1 (one) fully paid common share of the capital stock
of Marconi-Exportel, representing in the aggregate point zero one percent (.01%)
of the total capital stock of Marconi-Exportel, and evidenced by share
certificate listed in Annex "A" hereto under the name "Marconi-Networks Mexican
Subsidiaries Shares".

         (The shares of stock owned by each of Marconi-Networks in Marconi-Mex,
Administrativa-Marconi, Marconi-Com-Mexico and Marconi-Exportel which are
described in subparagraphs (i) to (iv) hereinabove, shall be hereinafter
designated collectively, as the "Marconi-Networks Mexican Subsidiaries Shares",
and the Marconi-Mex Shares, together with the Marconi-Mex Subsidiaries Shares
and the Marconi-Networks Mexican Subsidiaries Shares (but excluding the shares
to be evidenced by the Replacement Share Certificates only until such shares
have been pledged in terms of Clause First (d) hereinbelow), shall be designated
collectively as the "Pledged Shares", and in their capacity as issuers of the
Pledged Shares (which in due course, will include the shares evidenced by the
Replacement Share Certificates), Marconi-Mex, Administrativa-Marconi,
Marconi-Com-Mexico and Marconi-Exportel, shall be designated collectively as the
"Issuer Companies" and individually as an "Issuer Company").

         (b) Except for the pledge to be created in terms hereof, the
Marconi-Networks Mexican Subsidiaries Shares are free from any Security.

         NOW, THEREFORE, the parties hereto hereby agree as follows:

                                  C L A U S E S

         FIRST.- Creation of the Pledge. (a) Marconi-US, as continuing security
for the payment of the Secured Obligations, hereby agrees and shall be bound, in
regards to the Shares Missing to promptly pledge the Shares Missing as provided
in paragraph (d) hereunder and to record such promise to pledge with the
Secretary of the Board of Marconi-Mex, and to further abstain from incurring in
any act or omission which can adversely affect the rights of the Secured
Creditors under this promise to pledge or otherwise create a commitment, lien,
encumbrance or attachment in favor of or from third parties in respect of the
Shares Missing, and further agrees that upon the pledge of the Shares Missing,

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such pledge will constitute a first priority security interest in favor of, and
for the benefit of the Secured Creditors (as their respective interests may
exist with respect to the Secured Obligations) on all of the Marconi-Mex Shares,
to thereby secure the performance of all Secured Obligations, when due, and
therefore also payment when due (whether by stated maturity, redemption,
acceleration or otherwise), as the case maybe, of all amounts, including
principal of, interest on, fees related to, and premiums and additional amounts,
if any, relating to the Secured Obligations.

                  (b) Marconi-Mex, as continuing security for the payment of the
Secured Obligations, hereby creates a pledge and first priority security
interest in favor of, and for the benefit of the Secured Creditors (as their
respective interests may exist with respect to the Secured Obligations) on all
of the Marconi-Mex Subsidiaries Shares, to thereby secure the performance of all
Secured Obligations, when due, and therefore also payment when due (whether by
stated maturity, redemption, acceleration or otherwise), as the case maybe, of
all amounts, including principal of, interest on, fees related to, and premiums
and additional amounts, if any, relating to the Secured Obligations.

                  (c) Marconi-Networks, as continuing security for the payment
of the Secured Obligations, hereby creates a pledge and first priority security
interest in favor of, and for the benefit of the Secured Creditors (as their
respective interests may exist with respect to the Secured Obligations) on all
of the Marconi-Networks Mexican Subsidiaries Shares, to thereby secure the
performance of all Secured Obligations, when due, and therefore also payment
when due (whether by stated maturity, redemption, acceleration or otherwise), as
the case maybe, of all amounts, including principal of, interest on, fees
related to, and premiums and additional amounts, if any, relating to the Secured
Obligations.

                  (d) Marconi-US hereby undertakes and agrees to (i) promptly,
but in any case within the next twenty one (21) Business Days following the date
of execution hereof, initiate and thereafter diligently prosecute the
corresponding Shares Replacement Procedure seeking an order from a competent
court to have Marconi-Mex issue the Replacement Share Certificates, and (ii) as
soon as practicable, but in any case within the five (5) Business Days after the
issuance of such court order authorizing the Replacement Share Certificates, to
pledge for the benefit of the Secured Creditors the Shares Missing evidenced by
the Replacement Share Certificates, which Shares Missing should be fully paid
when pledged as provided herein, to thereby secure the Secured Obligations under
the terms of this Pledge of Shares Agreement, and such new pledge shall be
perfected in accordance with the terms of Clause Second hereinbelow (and
subsequently, as of such date of pledging the Shares Missing evidenced by the
Replacement Share Certificates, such Shares Missing so pledged, shall constitute
and be deemed to be included in the term "Pledged Shares" under this Pledge of
Shares Agreement for all purposes herein).

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                  (e) For the purposes agreed hereinabove, each of the Pledgors
hereby acknowledges and agrees that the Security Trustee is the lawful agent and
attorney in-fact of the Secured Creditors, with the authority to act on their
behalf and for their benefit in this Pledge of Shares Agreement and to enforce
this Agreement, without therefore requiring any manner of proxy or power of
attorney, and by execution of this Pledge of Shares Agreement the Pledgors
recognize without reservation the legal standing of the Security Trustee as
herein described.

                  (f) This Pledge of Shares Agreement and the pledges created or
to be created in terms of this Clause First shall not extend to or include or
secure any liability or sum which would, but for this proviso, cause this Pledge
of Shares Agreement to be unlawful or prohibited by any applicable law.

                  (g) To the extent permitted by applicable law, the Pledgors
hereby agree and shall be bound to the effect that the pledges created herein
will remain in full force and effect notwithstanding any amendments or
variations from time to time made by the parties thereto to the Relevant
Documents, with or without the consent of the Pledgors, and all references to
the Relevant Documents in this Pledge of Shares Agreement shall be understood to
relate to the Relevant Documents as amended or varied from time to time
(including, without limitation, any increase in the amount of the Secured
Obligations).

                  (h) Marconi-US hereby acknowledges and agrees to provide upon
request from the Security Trustee (not more than once a month), a written
progress report as to the status of the Shares Replacement Procedure being
prosecuted by Marconi-US, and providing an estimate as to the date when the
pledge on the Marconi-Mex shares to be evidenced by the Replacement Share
Certificates shall be satisfied and completed.

         SECOND.- Perfection of the Pledge. The pledges created hereby
(collectively called the "Pledges" and individually, a "Pledge") are perfected
pursuant to the terms of Article 334 of the General Law Governing Credit
Instruments and Transactions ("Ley General de Titulos y Operaciones de Credito",
hereinafter the "LGTOC"), as follows:

                  (a) By the endorsement in guaranty ("endoso en garantia") for
the benefit of the Secured Creditors of the Replacement Share Certificates
evidencing the Marconi-Mex Shares which will be performed by Marconi-US upon
completion of the Shares Replacement Procedure and the issuance of the
Replacement Share Certificates as agreed and accepted in terms of paragraph (d)
of Clause First above;

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                  (b) By the endorsement in guaranty ("endoso en garantia") of
the share certificates evidencing the Marconi-Mex Subsidiaries Shares which is
hereby made by Marconi-Mex for the benefit of the Secured Creditors;

                  (c) By the endorsement in guaranty ("endoso en garantia") of
the share certificates evidencing the Marconi-Networks Mexican Subsidiaries
Shares which is hereby made by Marconi-Networks for the benefit of the Secured
Creditors;

                  (d) By the delivery of the endorsed share certificates
evidencing the Pledged Shares to the Security Trustee (or its Delegate), in its
capacity as agent and attorney in fact for the Secured Creditors for the benefit
and on behalf of the Secured Creditors;

                  (e) By the registration of the promise to pledge referred to
in paragraph (a) above and of the actual Pledges and security interests created
hereby over the corresponding Pledged Shares, in each Issuer Company's stock
ledger, which registration is made simultaneously herewith by the Secretary of
the Board of Directors of the corresponding Issuer Company;

                  (f) By the delivery to the Security Trustee of a certificate
issued simultaneously herewith by the Secretary of the Board of Directors of
each Issuer Company of the corresponding Pledged Shares, stating that the
relevant registration mentioned in paragraph (e) above has been made, as
evidenced, in the case of the actual Pledges herein created, by the certificate
of the Secretary of the Board of Directors of each Issuer Company attached
hereto as Annex "B"; and for the Missing Shares, on the date when the shares
evidenced by the Replacement Share Certificates are pledged as provided for in
Clause First (d) hereinabove.

                  (g) The Pledgors and the Security Trustee hereby agree that,
upon the delivery to or to the order of the Security Trustee of the certificates
representing the Pledged Shares in terms of paragraph (d) above, the Security
Trustee will deliver to the Pledgors, a certificate in receipt of such share
certificates for the purposes provided in Article 337 of the LGTOC,
substantially in the form provided in Annex "C" attached hereto.

         THIRD.- Voting Rights of Pledged Shares. The Pledges created hereunder,
shall be subject to the following specific terms and conditions :

                  (a) Until such time as the Security Trustee has given a notice
in writing to the Pledgors stating that an Enforcement Event (as such term is
defined hereinabove) has occurred and is continuing, which notice shall be
prepared pursuant to the model attached hereto as Annex "D" (the "ST Notice of
Enforcement"), and which notice will be notarized in the jurisdiction of the

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                                       11

domicile of the Security Trustee and delivered to each Pledgor (with a copy to
the relevant Issuer Company), first by telefax at the number for each Pledgor
shown under its signature on the signature pages hereof, and thereafter by
overnight courier service, and/or in any other manner determined applicable by
the Security Trustee to ensure that each Pledgor (and the relevant Issuer
Company) receives its respective ST Notice of Enforcement, the Pledgors shall be
entitled to exercise all voting rights pertaining to their respective Pledged
Shares provided, however, that such voting rights may not be exercised by any of
the Pledgors in any manner which would constitute a Default or Event of Default
under the Indentures (as such terms are defined in the Indentures).

                  (b) For purposes of paragraph (a) above, in the event that no
ST Notice of Enforcement shall have been given and be effective and any of the
Pledgors gives ten (10) Business Days (as such term is defined in the
Intercreditor Agreement) prior written notice to the Security Trustee stating
that a shareholders' meeting of any of the Issuer Companies has been called,
then the Security Trustee shall execute and deliver (or cause to be executed and
delivered by the Delegate appointed for such purpose) to the relevant Pledgor
(with a copy to the relevant Issuer Company), a certificate substantially in the
terms set forth in the form which is attached as Annex "E" to this Pledge of
Shares Agreement, provided, that, if such notice of a shareholders' meeting
taking place is not given to the Security Trustee or if the same is not given
within the term specified above, the Security Trustee shall have no liability
whatsoever if any of the Pledgors are not able to exercise such voting rights at
such shareholders' meeting.

                  (c) In the event that as established in paragraph (a) above,
an ST Notice of Enforcement has been served on any of the Pledgors (with copy to
each relevant Issuer Company), each of the Pledgors hereby agrees to give and
maintain in full force and effect, and hereby grants the Security Trustee a
mandate to call for any shareholders' meetings of the relevant Issuer Companies
and to thereat vote the relevant Pledged Shares as it deems fit and such mandate
shall be deemed to be irrevocable during the life of this Pledge of Shares
Agreement because the mandate is issued as a means to ensure performance of the
obligations of each of the Pledgors in the Relevant Documents to secure the
Secured Obligations for the benefit of each Secured Creditor. The Pledgors
herein acknowledge that after an ST Notice of Enforcement has been served, the
Security Trustee shall be entitled to exercise (or refrain from exercising) all
voting rights pertaining to the Pledged Shares as provided for in the
Intercreditor Agreement and in terms consistent with applicable law.

                  (d) In accordance with the provisions of Article 338 of the
LGTOC, for so long as the Pledges created hereby are in force, all dividends
paid in connection with the Pledged Shares shall be released from this Pledge
and may

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be received directly by any of the Pledgors, as the case may be, without thereby
in any manner implying a payment or novation of the Secured Obligations, except
in the event that an ST Notice of Enforcement has been issued and delivered by
the Security Trustee to the Pledgors (with a copy to the relevant Issuer
Company) as provided for in section (a) above, in which case, dividends paid in
connection with the Pledged Shares as from the date on which such ST Notice of
Enforcement is given shall be subject to the Pledge hereby created and shall be
delivered by the relevant Issuer Company to the Security Trustee and applied (if
and when necessary) to the payment of the Secured Obligations, as set forth in
Clause Seventh below.

         FOURTH.- Redemption of Pledged Shares. Pursuant to Article 343 of the
LGTOC, the Pledgors agree that any amounts received by the Security Trustee, for
itself and/or on behalf of the Secured Creditors, or any amounts received by any
of the Pledgors directly, in redemption of the Pledged Shares pledged by the
relevant Pledgor, whether as a result of a capital stock decrease, the
liquidation of the relevant Issuer Company or otherwise, shall be applied in
accordance with the applicable provisions of the Relevant Documents.

         FIFTH.- New Shares. Each Pledgor hereby undertakes to pledge for the
benefit of the Secured Creditors, under the terms of this Pledge of Shares
Agreement, any new shares of the capital stock of any of the Issuer Companies or
options, warrants, convertible securities or any other rights to acquire shares
issued by any of the Issuer Companies which any of the Pledgors may acquire or
otherwise receive during the term of this Pledge of Shares Agreement, including,
without limitation, any new shares issued by such Issuer Company as a result of
stock dividends, a stock split, a reclassification, a readjustment or other
change to the capital structure of the corresponding Issuer Company, provided
that, such new shares or options, warrants, convertible securities and any other
rights to acquire additional shares shall be pledged for the benefit of the
Secured Creditors and such pledge shall be perfected in accordance with the
terms of Clause Second hereinabove, as soon as reasonably practicable, but in
any event, within the ten (10) Business Days next following the date such shares
or options, warrants, convertible securities and any other rights to acquire
additional shares are acquired or otherwise received by any of such Pledgors, as
the case may be, and such pledge of the new shares, options, warrants,
convertible securities or other rights to acquire additional shares shall be
made to secure the Secured Obligations.

         Upon receipt of a request from the Security Trustee, each Pledgor
herein expressly agrees to execute all necessary documentation in order to
create and perfect the pledge referred to in the above paragraph.

         SIXTH.- Enforcement of Pledge. Each Pledgor expressly agrees that the
Security Trustee, on behalf of the Secured Creditors, may judicially request the

<PAGE>

                                       13

sale of any of the Pledged Shares in terms of Article 341 of the LGTOC, if an ST
Notice of Enforcement has been delivered pursuant to the terms of Clause Third
(a) above of this Pledge of Shares Agreement.

         At any time after the occurrence of an Enforcement Event which is
continuing and the delivery by the Security Trustee of an ST Notice of
Enforcement as provided for in Clause Third (a) above, the security interest
created pursuant to this Pledge of Shares Agreement shall be immediately
enforceable and the Security Trustee may in its absolute discretion enforce all
or any part of the Pledges (at the times, in the manner and on the terms it
thinks fit) and exercise all or any of the powers, authorities and discretion
conferred on it by this Pledge of Shares Agreement or by law.

         SEVENTH.- Cash in Pledge. Each Pledgor expressly agrees that, in the
event that any amount in cash becomes pledged as provided for hereunder, title
to such amount in cash shall be transferred and conveyed in whole to the
Security Trustee as provided by Article 336 of the LGTOC, and as permitted
pursuant to Article 338 of the LGTOC, the Security Trustee shall have the right
to apply such amounts to the payment of the Secured Obligations in the order of
priority and ranking as provided for in the Intercreditor Agreement, and the
balance thereof, if any, shall be delivered to the corresponding Pledgor, in
accordance with written instructions from the relevant Pledgor. The Pledgors
herein acknowledge that upon the auction of the Pledged Shares the Security
Trustee shall have the right to bid, on behalf of the Secured Creditors for the
acquisition of the Pledged Shares in such auction procedures pursuant to
applicable law. The Security Trustee for itself as Secured Creditor and on
behalf of the other Secured Creditors, hereby expressly waives any and all
rights established in Article 340 of the LGTOC.

         EIGHTH.- Application of Proceeds. Any amounts derived from the
enforcement of the Pledges created hereunder, or otherwise, which under the
terms hereof are to be applied to the payment of the Secured Obligations, shall
be applied in the order of priority provided for in Schedule 4
(Post-Acceleration Payment Priorities) of the Intercreditor Agreement.

         NINTH.- Rights of Security Trustee. In connection with the Pledges
created pursuant to this Pledge of Shares Agreement, the Security Trustee shall
act at all times on behalf and for the benefit of the Secured Creditors, and in
accordance with the terms of the Intercreditor Agreement and this Pledge of
Shares Agreement.

         All of the rights and remedies hereunder will be exercised and enforced
exclusively by the Security Trustee for the benefit of the Secured Creditors and
no Secured Creditor shall have any right or remedy against the Pledgors

<PAGE>

                                       14

independently from the Security Trustee other than as permitted under the
Intercreditor Agreement.

         TENTH.- Notices. All notices provided for hereunder shall be in
writing, in the English language (or, in the case of all documents other than
notices given under or in connection with any Relevant Document, in English or,
if not in English, accompanied by an English translation thereof which, if
reasonably requested by the Security Trustee, shall be a certified translation)
and shall be delivered or sent to each party at its address or telefax number
(as applicable) set forth under such party's name on the signature pages hereof,
or at such other address or telefax number (as applicable) as shall be
designated by such party in written notice given to the other parties hereto.
All such notices and communications shall be effective, if delivered at the
address of the recipient, on the date following the date of its delivery, and if
sent by telefax, when the relevant receiving party shall issue an
acknowledgement of receipt thereof by telefax or otherwise in writing.

         ELEVENTH.- Language. This Pledge of Shares Agreement shall be executed
in the English and Spanish languages, both of which shall bind the parties
hereto and constitute but one and the same agreement and instrument, as the case
may be; provided, however, that in case of doubt as to the proper interpretation
or construction of this Pledge of Shares Agreement, the English text shall be
controlling in all cases, except in connection with any legal action or
proceeding brought in respect of this Pledge of Shares Agreement in the
competent courts of Mexico, or any political subdivision thereof, in which case
the Spanish text shall be controlling.

         TWELFTH.- Governing Law and Jurisdiction. The interpretation of, and
compliance with, this Pledge of Shares Agreement, shall be governed by the laws
applicable in the Federal District of Mexico, and each of the Pledgors expressly
submits to the competent courts of the Federal District of Mexico, expressly
waiving any other jurisdiction rights it may have by reason of its present or
future domicile, or otherwise and therefore each Pledgor designates as its
domicile to receive all manner of notices, including service of process, that
set forth under its name on the signature pages.

         THIRTEENTH.- No Implied Covenants. The Security Trustee undertakes to
perform such duties, and only such duties, as are specifically set forth in this
Pledge of Shares Agreement and in the Intercreditor Agreement, and no implied
covenants or obligations shall be read into this Agreement against the Security
Trustee.

         FOURTEENTH.- Amendments. This Pledge of Shares Agreement may not be
amended, discharged or terminated (other than a termination in terms of

<PAGE>

                                       15

Clause Sixteenth hereof) unless such amendment, discharge or termination is in
writing and signed by each of the parties hereto.

         The Pledgors hereby expressly acknowledge, recognize and agree that,
for all matters relating to or arising from or in connection with this Pledge of
Shares Agreement (i) the Security Trustee is acting in its capacity as agent and
attorney-in-fact for the Secured Creditors, (ii) the Security Trustee has all
necessary legal capacity to act on behalf and for the benefit of the Secured
Creditors, and (iii) the Security Trustee when acting hereunder, shall be acting
in accordance with and subject to the terms of the Intercreditor Agreement.

         FIFTEENTH.- Counterparts. This Pledge of Shares Agreement may be
executed in any number of counterparts, each of which shall be deemed to be an
original, but all such counterparts shall together constitute but one and the
same instrument.

         SIXTEENTH.- Term and Release of Pledge. The Pledges which are being
created hereby shall be in full force and effect for so long as any of the
Secured Obligations, for each relevant Pledgor, remain outstanding and up to the
date on which all Secured Obligations of each relevant Pledgor are irrevocably
paid and discharged in full or until the security is released pursuant to the
terms of Clause 5 of the Intercreditor Agreement.

         If instructed or requested and permitted to release the Pledge pursuant
to the terms and subject to the conditions and circumstances set out in the
Intercreditor Agreement, and without recourse to, or any representation or
warranty by, the Security Trustee or any of its nominees, the Security Trustee
agrees to promptly but in any case within the 10 (ten) Business Days following
receipt of such instruction or request, deliver to the Pledgors at their cost
(i) a certificate of discharge, releasing the Pledges created hereunder, (ii) a
notice to each Issuer Company informing of such release and requesting that the
registration established in Clause Second, paragraph (e) of this Pledge of
Shares Agreement be cancelled, (iii) the original endorsed share certificates
evidencing the Pledged Shares initially delivered to the Security Trustee (or
its Delegate), as provided in Clause Second, paragraph (d) of this Pledge
Agreement, and (iv) any other share certificate or other documents delivered to
the Security Trustee (or to its Delegate) by the Pledgors pursuant to Clause
Fifth of this Pledge of Shares Agreement.

         SEVENTEENTH.- Assignment. The Pledgors may not assign nor transfer
their rights and obligations hereunder to any third party without the prior
written consent of the Security Trustee.

<PAGE>

                                       16

         The Security Trustee may cause another person to become a party to this
Pledge of Shares Agreement in its place in accordance with the terms and
provisions contained in the Intercreditor Agreement.

         The Security Trustee shall be entitled to disclose such information
concerning the Pledgors and this Pledge of Shares Agreement as the Security
Trustee considers appropriate to any actual or proposed direct or indirect
successor or to any person to whom information may be required to be disclosed
by any applicable law.

         EIGHTEENTH.- Expenses and Costs, Taxes. Each Pledgor hereby agrees and
shall be obligated to pay in relation to such Pledgor on the date hereof, and
from time to time on demand by the Security Trustee acting as agent for the
Secured Creditors, and on a full indemnity basis, any and all reasonable and
documented legal or other costs and expenses (including any legal fees) and any
applicable Taxes (including any value added tax) incurred by the Security
Trustee and/or any of the Secured Creditors in relation to, or derived from, (i)
the execution, perfection, release and discharge of this Pledge of Shares
Agreement and the Pledges created in terms herein; (ii) the actual or
contemplated exercise, preservation and/or enforcement of any of the rights,
powers and remedies of, or the performance of the duties and obligations of any
of the Secured Creditors, the Security Trustee or any Delegate with respect to
this Pledge of Shares Agreement or to the Security created or intended to be
created in terms hereof, or with respect to any amendment or waiver in
connection with this Pledge of Shares Agreement; (iii) the preservation of the
Security created or intended to be created in respect of the Pledged Shares; and
(iv) any enforcement procedure brought in connection with the Pledges created in
terms hereof or with this Pledge of Shares Agreement with respect to or in
relation to any Pledgor, and all such payment obligations constitute, and shall
be deemed to be, Secured Obligations as such term is used and defined in this
Pledge of Shares Agreement, and therefore also secured by the Pledges created
hereunder with respect to such Pledgor.

         In the event that such costs and expenses cannot be attributed to a
specific Pledgor, then such costs and expenses shall be borne pro-rata by each
Pledgor.

         Each Pledgor shall promptly pay on demand by the Security Trustee as
agent for the Secured Creditors, any stamp, registration, notarial and other
similar Taxes or fees applicable and or required under Mexican Law, which are
paid or payable by the Security Trustee acting as agent for the Secured
Creditors in connection with any action taken or contemplated by or on behalf of
the Security Trustee in such capacity, for perfecting, enforcing, releasing,
cancelling, reassigning or resolving any doubt concerning, or for any other
purposes in relation to this Pledge of Shares Agreement, any amendment thereto,
any

<PAGE>

                                       17

transfer and/or assignment of the rights and/or obligations under the same, or
the Pledges created or intended to be created in respect of the Pledged Shares,
including the promise to pledge the Missing Shares referred to in Clause First
(a) hereof, and the Shares Replacement Procedure referred to in Clause First (d)
and (h) above, and shall, from time to time, indemnify the Security Trustee
promptly on demand against any liabilities, costs, claims, and expenses
resulting from any failure to pay by any Pledgor or any delay by any Pledgor in
paying any such Taxes or fees.

         NINETEENTH.- Headings. The parties herein agree and acknowledge that
title headings of Clauses used herein, are for reference only and have no
purpose other than the convenience of the parties and therefore, shall not
affect the construction or interpretation hereof.

         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed by their respective officers or agents thereunto duly authorized, on
the date and place set-forth below.

                                 THE "PLEDGORS"

                           MARCONI COMMUNICATIONS INC.

                                  WILL JOHNSON

                           ---------------------------------------
                           By:        WILL JOHNSON
                           Title:     ATTORNEY
                           Address:   Marconi Communications, Inc.
                                      c/o Marconi Inc.
                                      333 Pierce Road, Suite 370
                                      Itasca, Illinois 60143 USA

                           Telefax:   (630) 285-1514
                           Attn:      Patricia Hoffman
                           Telephone: (630) 285-5303

                           Date and   19 MAY 2003
                           Place of   LONDON
                           Signature: _____________________

<PAGE>

                                       18

                      MARCONI COMMUNICATIONS, S.A. DE C.V..

                                 T.C.R. SHEPHERD

                           --------------------------------
                           By:           T.C.R. SHEPHERD
                           Title:        ATTORNEY
                           Address:      No. 60 Parque de Amargua,
                                         Col. Parques de la Herradura
                                         Huixquilucan, Edo. de Mexico
                                         C.P. 52785

                           Telefax:      5255 5293-3610
                           Attn:         Mr. Rafael Diez / Eduardo Lopez
                           Telephone:    5255 5293-8302

                           with copy to: Mr. Armando Cuesta
                           Telefax:      (954) 659-3939
                           Telephone:    (954) 659-3910

                           Date and      19 MAY 2003
                           Place of      LONDON
                           Signature:    _____________________

                        MARCONI NETWORKS WORLDWIDE, INC.

                                 T.C.R. SHEPHERD

                           -----------------------------
                           By:           T.C.R. SHEPHERD
                           Title:        ATTORNEY
                           Address:      Marconi Networks Worldwide, Inc.
                                         c/o Marconi Inc.
                                         333 Pierce Road, Suite 370
                                         Itasca, Illinois 60143 USA

                           Telefax:      (630) 285-1514
                           Attn:         Patricia Hoffman
                           Telephone:    (630) 285-5303

                           Date and      19 MAY 2003
                           Place of      LONDON
                           Signature:    _____________________

<PAGE>

                                       19

                             THE "SECURITY TRUSTEE"

                   THE LAW DEBENTURE TRUST CORPORATION p.l.c.

                                    R D RANCE

                           -----------------------------
                           By:           R D RANCE
                           Title:        Director

                           Address:      100 Wood Street Fifth Floor
                                         London EC2V7EX

                           Telefax:      + 4420 7696 5261
                           Attn:         Manager, Trust Administration
                           Telephone:    + 4420 7606 5451

                           Date and      19 MAY 2003
                           Place of      LONDON
                           Signature:    _____________________

<PAGE>

                        LIST OF ANNEXES TO THIS AGREEMENT

         "A" LIST OF PLEDGED SHARES

         "B" COPY OF ISSUER COMPANY'S SECRETARY CERTIFICATE

         "C" FORM OF PLEDGED SHARES RECEIPT

         "D" FORM OF ST NOTICE OF ENFORCEMENT

         "E" FORM OF CERTIFICATE OF SHARES IN DEPOSIT

<PAGE>

                                    ANNEX "A"

                             LIST OF PLEDGED SHARES

A.       MARCONI-US MEXICAN SUBSIDIARY:

-        Share certificate No. 1 evidencing 650 common shares, no par value,
         representing the capital stock of Marconi Communications, S.A. de C.V.,
         under the name of Marconi Communications Inc.

-        Share certificate No. 2 evidencing 349 common shares, no par value,
         representing the capital stock of Marconi Communications, S.A. de C.V.,
         under the name of Marconi Communications Inc.

B.       MARCONI-MEX SUBSIDIARIES SHARES:

-        Share certificate No. 1 dated April 27, 2003 evidencing 7'742,816
         common shares, with a par value of $1.00 Peso each share, representing
         the capital stock of Administrativa Marconi Communications, S.A. de
         C.V., under the name of Marconi Communications, S.A. de C.V.

-        Share certificate No. 13 dated April 27, 2003 evidencing 999 common
         shares, with a par value of $1.00 Peso each share, representing the
         capital stock of Administrativa Marconi Communications, S.A. de C.V.,
         under the name of Marconi Communications, S.A. de C.V.

-        Share certificate No. 1 dated April 27, 2003 evidencing 440'723,746
         common shares, with a par value of $0.10 Peso each share, representing
         the capital stock of Marconi Communications de Mexico, S.A. de C.V.,
         under the name of Marconi Communications, S.A. de C.V.

-        Share certificate No. 21 dated April 27, 2003 evidencing 1,249 common
         shares, with a par value of $0.10 Peso each share, representing the
         capital stock of Marconi Communications de Mexico, S.A. de C.V., under
         the name of Marconi Communications, S.A. de C.V.

-        Share certificate No. 1 dated April 27, 2003 evidencing 65,000 common
         shares, no par value, representing the capital stock of Marconi
         Communications Exportel, S.A. de C.V., under the name of Marconi
         Communications, S.A. de C.V.

<PAGE>

                                       2

-        Share certificate No. 6 dated April 27, 2003 evidencing 999 common
         shares, no par value, representing the capital stock of Marconi
         Communications Exportel, S.A. de C.V., under the name of Marconi
         Communications, S.A. de C.V.

C.       MARCONI-NETWORKS MEXICAN SUBSIDIARIES SHARES:

-        Share certificate No. 4 dated April 27, 2003 evidencing 1 common share,
         no par value, representing the capital stock of Marconi Communications,
         S.A. de C.V., under the name of Marconi Networks Worldwide, Inc.

-        Share certificate No. 14 dated April 27, 2003 evidencing 1 common
         share, with a par value of $1.00 Peso each share, representing the
         capital stock of Administrativa Marconi Communications, S.A. de C.V.,
         under the name of Marconi Networks Worldwide, Inc.

-        Share certificate No. 22 dated April 27, 2003 evidencing 1 common
         share, with a par value of $0.10 Peso each share, representing the
         capital stock of Marconi Communications de Mexico, S.A. de C.V., under
         the name of Marconi Networks Worldwide, Inc.

-        Share certificate No. 7 dated April 27, 2003 evidencing 1 common share,
         no par value, representing the capital stock of Marconi Communications
         Exportel, S.A. de C.V., under the name of Marconi Networks Worldwide,
         Inc.

<PAGE>

                                    ANNEX "B"

                          [ISSUER COMPANY'S LETTERHEAD]

                                   CERTIFICATE

I____________________ in my capacity of Secretary of the Board of Directors of
[NAME OF ISSUER COMPANY] S.A. de C.V. (the "Company"), hereby certify the
following:

That pursuant to article 334 of the General Law Governing Credit Instruments and
Transactions ("LGTOC"), the pledge created with respect to ______________ shares
representing the capital stock of the "Company" (the "Pledged Shares") owned BY
[NAME OF SHAREHOLDER OF RECORD AND PLEDGOR], pursuant to the Pledge of Shares
Agreement, dated as of __________ 2003 (the "Pledge of Shares Agreement"),
executed by Marconi Communications Inc., Marconi Communications S.A. de C.V.,
and Marconi Networks Worldwide, Inc., as pledgors and The Law Debenture Trust
Corporation p.l.c., in its capacity as agent and attorney-in fact acting on
behalf and for the benefit of the Secured Creditors therein mentioned, has been
duly registered in the Stock Registry book of the Company in favor of the
Secured Creditors referred to in such Pledge of Shares Agreement and that the
voting rights pertaining to such Pledged Shares should be exercised in
accordance with the terms of the Pledge of Shares Agreement..

                             Dated _________, 2003.

                             ______________________.
                                     (name)
                       Secretary of the Board of Directors
                           of [NAME OF ISSUER COMPANY]

<PAGE>

                                    ANNEX "C"

              FORM OF CERTIFICATE IN RECEIPT OF THE PLEDGED SHARES

         (LETTERHEAD OF THE SECURITY TRUSTEE OR ITS APPOINTED DELEGATE)

                                                          Date [______], 20[__].
To: [NAME OF THE RELEVANT PLEDGOR]
Address: [ ______________]
Telefax: [_____________]

Attention: [_________________]

                       Re.: Receipt of the Pledged Shares.

Dear Sirs:

We refer to the Pledge of Shares Agreement dated as of ________, 2003, by and
among (i) Marconi Communications Inc., Marconi Communications, S.A. de C.V., and
Marconi Networks Worldwide, Inc. (all the foregoing collectively the
"Pledgors"), and (ii) The Law Debenture Trust Corporation p.l.c., as agent and
attorney-in-fact, acting on behalf and for the benefit of the Secured Creditors
therein identified (the "Shares Pledge Agreement"). Except to the extent
otherwise defined herein, all capitalized terms used in this Certificate shall
have the same meaning attributed to them in the Shares Pledge Agreement.

Pursuant to the provisions of Clause Second, paragraph (g) of the Shares Pledge
Agreement, the undersigned acting on behalf and for the benefit of the Secured
Creditors, [The Law Debenture Trust Corporation, p.l.c./Appointed Delegate]
hereby acknowledge having received from you, acting as Pledgor, the following
original certificates/titles of shares:

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------
CERTIFICATE NO.                 ISSUER COMPANY                 NUMBER OF SHARES
-------------------------------------------------------------------------------
<S>                             <C>                            <C>
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
</TABLE>

<PAGE>

This Certificate is issued for the purposes established in Article 337 of the
LGTOC.

                                   Sincerely,

                  [The Law Debenture Trust Corporation p.l.c.]
                      acting on behalf and for the benefit
                       of the Secured Creditors [Delegate]

                             _______________________
                             By:
                             Title:

<PAGE>

                                    ANNEX "D"

                        FORM OF ST NOTICE OF ENFORCEMENT

                      (LETTERHEAD OF THE SECURITY TRUSTEE)

       [ONCE NOTARIZED, SEND A COPY VIA FAX, AND THE ORIGINAL VIA COURIER]

                                                          Date [______], 20[__].

To: [NAME OF THE RELEVANT PLEDGOR]
Address: [ ______________]
Telefax: [_____________]

Attention: [_________________]

                         Re.: ST Notice of Enforcement.

Dear Sirs:

We refer to (i) the Pledge of Shares Agreement dated as of ________, 2003, by
and among Marconi Communications Inc., Marconi Communications, S.A. de C.V., and
Marconi Networks Worldwide, Inc. (all the foregoing collectively the
"Pledgors"), and The Law Debenture Trust Corporation p.l.c., as agent and
attorney-in-fact, acting on behalf and for the benefit of the Secured Creditors
therein identified (the "Shares Pledge Agreement"), under which [____] shares of
stock of [INSERT NAME OF CORRESPONDING ISSUER COMPANY], have been pledged by you
(the "Pledged Shares"), and (ii) a notice from us to you dated [___], stating
that an Enforcement Event (as such term is defined in the Shares Pledge
Agreement) has occurred. Except to the extent otherwise defined herein,
capitalized terms used herein, shall have the same meaning attributed to them as
in the Shares Pledge Agreement.

Pursuant to the provisions set forth in Clause Third of the Shares Pledge
Agreement, and considering that an Enforcement Event has occurred, please be
advised that as of the date hereof, all voting rights pertaining to the Pledged
Shares are now transferred and passed on to the Security Trustee, acting on
behalf and for the benefit of the Secured Creditors, and therefore as of this
date any Shareholders' Meeting of the Issuer Company, that is called in terms of
its

<PAGE>

                                       2

by-laws, shall be attended (directly or through an attorney-in-fact appointed
for such purpose) by the Security Trustee.

The present ST Notice of Enforcement is issued to you with a copy to the
corresponding Issuer Company, for all legal purposes that may take place.

                                   Sincerely,

                  [The Law Debenture Trust Corporation, p.l.c.]
                      acting on behalf and for the benefit
                       of the Secured Creditors [Delegate]

                             _______________________
                             By:
                             Title:

In witness whereof, the foregoing notice was signed and ratified before me
[_____________], Notary Public in and for the County of [________] State of
[_______],[_____]; therefore, I set my hand and official seal hereunto on this
[___] day of [______], 20[__].

Notary Public

____________________
By:

My license expires on [______], 20[__].

Cc.:     [INSERT NAME OF THE RELEVANT ISSUER COMPANY]

<PAGE>

                                    ANNEX "E"

                          CERTIFICATE FOR ATTENDANCE TO
                              SHAREHOLDERS' MEETING

                      (LETTERHEAD OF THE SECURITY TRUSTEE)

To: [NAME OF THE RELEVANT
ISSUER COMPANY]
Address: [______________]
Telefax: [_____________]

Attention: Secretary of the Board
           of Directors.

Dear Sirs:

We refer to (i) the Pledge of Shares Agreement dated as of [________], 2003,
entered into by and among Marconi Communications Inc., Marconi Communications,
S.A. de C.V., and Marconi Networks Worldwide, Inc. all the foregoing in their
capacity as pledgors, and The Law Debenture Trust Corporation p.l.c., as agent
and attorney-in-fact acting on behalf and for the benefit of the Secured
Creditors therein identified (the "Shares Pledge Agreement"), and (ii) to a
notice received from [INSERT NAME OF RELEVANT PLEDGOR] (the "Owner"), where we
are informed that a Shareholders' Meeting of [INSERT NAME OF ISSUER COMPANY]
(the "Issuer Company"), has been called to take place on [INSERT SCHEDULED DATE
OF SHAREHOLDERS MEETING]. Unless otherwise defined herein, all capital terms
used herein, shall have the same meaning as that ascribed to them in the Shares
Pledge Agreement.

By means of this Certificate we confirm to you (i) that [The Law Debenture Trust
Corporation, p.l.c./Delegate] is holding on behalf and for the benefit of the
Secured Creditors the titles and/or certificates of shares identified
hereinbelow, representing the capital stock of the Issuer Company which are
subject to the Pledge created pursuant to the terms and for the purposes
established in the Shares Pledge Agreement (the "Pledged Shares"), which Pledge
is recorded in the Issuer Company's Shares Registry Book; and (ii) that unless
you receive notice to the contrary, the Owner may exercise all voting rights
pertaining to such Pledged Shares in the shareholders' meeting referred to
above.

<PAGE>

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------
TITLE/CERTIFICATE NO.       SERIES AND NO. OF SHARES           DATE OF ISSUANCE
-------------------------------------------------------------------------------
<S>                         <C>                                <C>
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
</TABLE>

This Certificate is issued on this date [____] of [_____], 200[_], for all legal
purposes and effects concerned.

                                  Respectfully,

                  [The Law Debenture Trust Corporation p.l.c.]
                      acting on behalf and for the benefit
                       of the Secured Creditors [Delegate]

                             _______________________
                             By:
                             Title: