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                                                                    EXHIBIT 4.83

                                                                  CONFORMED COPY

                                   PUBLIC DEED

                           Before me the notary public

              Carole Fontannaz, in Zug/Switzerland, Baarerstrasse 8

                                    appeared

                               on this 14 May 2003

Dr. Marc Nater, Attorney-at-Law, c/o WENGER PLATTNER, Goldbach-Center,
Seestrasse 39, CH-8700 Kusnacht ZH, not acting on his own name, but on the basis
of a power of attorney presented to the notary public, on behalf of

MARCONI COMMUNICATIONS B.V., Hoogoorddreef 9, 1101 BA, NL-Amsterdam-Zuidoost,

                                                     (hereinafter the "PLEDGOR")

                                       and

Micha Blattmann, Attorney-at-Law, Bar & Karrer, Baarerstrasse 8, CH-6301 Zug,
not acting on his own name, but on the basis of a substitution power of attorney
and on the basis of a power of attorney presented to the notary public, on
behalf of

THE LAW DEBENTURE TRUST CORPORATION P.L.C., Fifth Floor, 100 Wood Street, London
EC2V 7EX, United Kingdom

                                            (hereinafter the "SECURITY TRUSTEE")

The persons appearing, acting as described above, declared with the request for
notarisation:

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                                   PUBLIC DEED

                             SHARE PLEDGE AGREEMENT

                                     between

MARCONI COMMUNICATIONS B.V.,

a private company with limited liability (besloten vennootschap met beperkte
aansprakelijkheid) incorporated under the laws of The Netherlands, having its
seat at Gouda, The Netherlands and its registered office at Hoogoorddreef 9,
1101 BA, Amsterdam-Zuidoost, The Netherlands, registered with the Chamber of
Commerce in the Netherlands under number 29.04.66.60

                                                                 (the "PLEDGOR")

                                       and

THE LAW DEBENTURE TRUST CORPORATION P.L.C.
Fifth Floor
100 Wood Street
London EC2V 7EX

                                                        (the "SECURITY TRUSTEE")

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WHEREAS

A.       The Pledgor is the legal and beneficial owner of the entire share
         capital of Marconi Communications GmbH ("MC GMBH"), which consists of
         one share with a nominal value of CHF 100,000 ("Stammeinlage") (the
         "SHARE");

B.       The parties execute this agreement (this "AGREEMENT") in order to give
         the Secured Creditors security for the Secured Obligations.

NOW, THEREFORE, in consideration of the mutual convenants herein contained, the
Parties hereto agree as follows:

1.       INTERPRETATION

         In this Agreement the following terms have the following meanings:

         "AGREEMENT" has the meaning given to it in the Preamble.

         "CONTINUING" in relation to an Enforcement Event, shall be construed as
         a reference to an acceleration of any Secured Obligation (other than
         Secured Obligations arising under the New Bonding Facility Agreement)
         where such acceleration has not been rescinded in writing or a
         declaration that the Secured Obligations (other than Secured
         Obligations arising under the New Bonding Facility Agreement) are
         prematurely due and payable (other than solely as a result of it
         becoming unlawful for a Secured Creditor to perform its obligations
         under the Relevant Documents) where such declaration has not been
         revoked in writing or any failure by an Obligor to pay any principal
         amount in respect of any Secured Obligations (other than Secured
         Obligations arising under the New Bonding Facility Agreement) whether
         on maturity or otherwise which has not been remedied or waived in
         writing. For the purposes of this definition of "continuing", the
         definition of "Secured Obligations" shall have the same meaning as in
         the Intercreditor Deed.

         "DUTCH GUARANTEES" means the following guarantees issued by, amongst
         others, the Pledgor: (i) the senior note guarantee dated on or about
         the date hereof issued in accordance with the provisions of the Senior
         Note Indenture, (ii) the junior note guarantee dated on or about the
         date hereof issued in accordance with the provisions of the Junior Note
         Indenture and (iii) the composite guarantee issued in connection with,
         inter alia, the provisions of the New Bonding Facility Agreement;

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         all these guarantees are subject to the guarantee limitation set out in
         clause 5 of Schedule 9 (Dutch Guarantee Limitation) of the
         Intercreditor Deed.

         "INTERCREDITOR DEED" means the security trust and intercreditor deed to
         be dated on or about 19 May 2003 and made between, amongst others,
         Marconi Corporation plc as Issuer, The Law Debenture Trust Corporation
         p.l.c. as Security Trustee, Law Debenture Trust Company of New York as
         Senior Note Trustee, JPMorgan Chase Bank as Junior Note Trustee, HSBC
         Bank plc as New Bonding Facility Agent and The Bank of New York as
         Depository, Paying Agent and Registrar.

         "RELEVANT DOCUMENTS" shall have the meaning given to it in the
         Intercreditor Deed, 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).

         "SECURED OBLIGATIONS" means all obligations at any time owing or
         incurred by the Pledgor to any Secured Creditor under any of 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:

         (a)      any refinancing, novation, deferral or extension;

         (b)      any obligation relating to any increase in the amount of such
                  obligations;

         (c)      any claim for damages or restitution; and

         (d)      any claim as a result of any recovery by an Obligor of a
                  payment or discharge, or non-allowability, on the grounds of
                  preference,

         and any amounts that would be 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); all the above
         obligations are, for the avoidance of doubt, subject to the limitation
         set forth in clause 5 of Schedule 9 (Dutch Guarantee Limitation) of the
         Intercreditor Deed.

         "SHARE" has the meaning given to it in the Preamble.

         "MC GMBH" has the meaning given to it in the Preamble.

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         Unless defined herein, defined terms shall bear the same meanings as in
         the Intercreditor Deed.

2.       PLEDGE

2.1.     As security for the Secured Obligations, the Pledgor hereby pledges to
         the Security Trustee acting for the benefit of itself and for the
         benefit of the other Secured Creditors:

         (a)      the Share and all ancillary rights and claims pertaining
                  thereto, including claims for dividends, other benefits or
                  profit distributions, capital repayments, pre-emptive rights,
                  as well as the claims for liquidation proceeds; and

         (b)      all additional shares in MC GmbH from time to time acquired by
                  the Pledgor in any manner (including by way of capital
                  increases) and all aforesaid claims relating thereto
                  (hereinafter included when referring to the "Share").

2.2.     Within 10 (ten) Business Days of the Issue Date, the Pledgor shall
         deliver to the Security Trustee the following documents:

         (a)      a certified true copy of the resolution of MC GmbH's partners'
                  meeting acknowledging the pledging of the Share in favour of
                  the Security Trustee; and

         (b)      a certified true copy of MC GmbH's share register evidencing
                  the existence of the pledge in favour of the Security Trustee.

3.       REPRESENTATIONS

         The Pledgor represents and warrants to the Security Trustee that:

3.1.     it is the sole legal and beneficial owner of the Share free from any
         Security except as created by this Agreement; and

3.2.     the Share is fully paid up.

4.       UNDERTAKINGS

4.1.     The Pledgor undertakes to the Security Trustee to the extent not
         already effectuated by virtue of Clause 2.1(b) hereof, to pledge
         hereunder, within 10 (ten) Business Days of its acquisition thereof,
         any and all additional shares of stock or other securities of MC GmbH.

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4.2.     The Pledgor undertakes to the Security Trustee that at any time and
         from time to time, at its own expense, it will promptly take all action
         or execute all such documents (including assignments, transfers,
         charges, notices and instructions) that the Security Trustee may
         request, in order to perfect the security interest granted or purported
         to be granted hereby or for the exercise of all rights, powers and
         remedies of the Security Trustee provided by or pursuant to this
         Agreement or by law and/or to facilitate the realisation of the Share.

4.3.     If so requested by the Security Trustee the Pledgor shall take all such
         action as is available to it (including making all filings and
         registrations) as may be necessary for the purpose of the creation,
         perfection or maintenance of any security conferred or intended to be
         conferred on the Security Trustee by or pursuant to this Agreement.

4.4.     The Pledgor shall, except as not expressly prohibited under the terms
         of the Indentures, not:

         (a)      create or permit to arise any mortgage, charge, lien or other
                  security interest on the Share or any interest in or part of
                  the Share; or

         (b)      sell or attempt to sell or otherwise dispose of the Share or
                  any interest in or part of the Share.

5.       DURATION AND RELEASE

5.1.     Unless the pledge ceases to exist by operation of law, the pledge
         created hereunder and this Agreement shall remain in full force and
         effect until the date on which the Security Trustee releases the pledge
         hereunder. The Security Trustee shall, at the cost of the Pledgor,
         release and cancel the security constituted by this Agreement and
         procure the reassignment to the Pledgor of the property and assets
         assigned to the Security Trustee pursuant to this Agreement in
         accordance with the terms and subject to the conditions and
         circumstances set out in the Intercreditor Deed and without recourse
         to, or any representation or warranty by, the Security Trustee or any
         of its nominees.

5.2.     This security is in addition to any existing or future collateral,
         guarantee or other security held by the Security Trustee or any of the
         Secured Creditors.

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5.3.     The Pledge created hereunder shall only be released by operation of law
         or in accordance with the terms and subject to the conditions and
         circumstances set out in the Intercreditor Deed.

6.       VOTING RIGHTS

6.1.     The Pledgor shall be entitled to exercise any and all membership rights
         pertaining to the Share, including, without limitation, the right to
         vote in the general meeting of MC GmbH provided, however, that the
         Pledgor shall not exercise or refrain from exercising any such right if
         such action would constitute a Default or Event of Default ( in each
         case as such term is defined in the Indentures).

6.2.     Upon the occurrence of an Enforcement Event which is continuing, the
         Pledgor shall exercise the membership rights conferred by the Share,
         including, without limitation, the right to vote in the general meeting
         of MC GmbH in accordance with the instructions received from the
         Security Trustee. The Pledgor shall forthwith inform the Security
         Trustee about the exercise of the membership rights.

7.       DIVIDENDS

7.1.     Subject at all times to the restrictions set forth in the Indentures,
         any payment of dividends or other payments by MC GmbH relating to the
         Share and claims pledged under this Agreement shall be made to the
         Pledgor, provided no Enforcement Event which is continuing has
         occurred.

7.2.     Upon the occurrence of an Enforcement Event which is continuing, any
         payment of dividends or other payments by MC GmbH relating to the Share
         and claims pledged under this Agreement shall be made to the Security
         Trustee and applied by the same in satisfaction of the Secured
         Obligations as provided under, and subject to the terms of, the
         Intercreditor Deed.

7.3.     Similarly, upon occurrence of an Enforcement Event and at any time
         thereafter whilst such Enforcement Event is continuing, any and all:

         (a)      dividends and interest paid or payable other than in cash in
                  respect of, and instruments and other property received,
                  receivable or otherwise distributed in respect of, or in
                  exchange for, the Share;

         (b)      dividends and other distributions paid or payable in cash in
                  respect of the Share in connection with a partial or total
                  liquidation or dissolution or in connection with a reduction
                  of capital, capital surplus or paid-in-surplus; and

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         (c)      cash paid, payable or otherwise distributed in respect of
                  principal (nominal value/stated capital) of, or in redemption
                  of, or in exchange for, the Share,

         shall be exclusively made and/or paid to the Security Trustee and
         applied in satisfaction of the Secured Obligations as provided under,
         and subject to the terms of, the Intercreditor Deed.

8.       ENFORCEMENT

8.1.     At any time after the occurrence of an Enforcement Event and the
         Security Trustee (acting on instructions received pursuant to the terms
         of the Intercreditor Deed) giving notice to the Issuer thereof, the
         pledge created hereunder shall become immediately enforceable and the
         Security Trustee:

         (a)      shall be entitled (but not bound) to dispose of the Share by
                  way of private sale ("Selbstverkaufsrecht"), without having to
                  initiate proceedings under the applicable statutory laws; and

         (b)      shall be at liberty, notwithstanding the foregoing and the
                  provisions of Art. 41 of the Swiss Federal Law on the Recovery
                  of Debts and Bankruptcy or any other applicable law, to
                  institute and pursue the ordinary procedure for recovery of
                  debt without having first to dispose of the Share or to
                  institute statutory proceedings for the realization thereof,

         provided always that any proceeds likewise realized shall be applied as
         set out in the Intercreditor Deed.

8.2.     With a view to the Security Trustee exercising its right pursuant to
         Clause 8.1, the Pledgor hereby assigns and transfers the Share, with
         all rights and obligations thereto pertaining, to such third party as
         the Security Trustee may designate, subject to the condition that this
         assignment and transfer shall become effective automatically when and
         if the Pledgor receives a notarised statement of the third party
         acquiror of its express acceptance of this assignment and transfer,
         accompanied by a notarised statement of the Security Trustee
         confirming:

         (a)      the occurrence of an Enforcement Event;

         (b)      that the Security Trustee is entitled and has decided to
                  enforce the pledge granted pursuant to this Agreement by way
                  of private sale;

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         (c)      the purchase price which will be paid by the third party
                  acquiror for the Share; and

         (d)      that the third party acquiror having delivered the
                  aforementioned notarised statement of acceptance is the party
                  to which the Security Trustee has sold the Share pursuant to
                  Clause 8.1 hereof.

8.3.     Receipt of the aforesaid statements shall be reconfirmed by the Pledgor
         and shall be deemed validly effected with the elapse of 20 (twenty)
         Business Days from the time the statement as per Clause 8.2 has been
         delivered to the Pledgor together with the statement of the acquirer,
         by registered mail for express/special delivery and addressed to the
         Pledgor at the address as per Clause 11.8 hereof.

8.4.     The purchase price paid for any Share disposed of in accordance with
         Clause 8.1(a) shall correspond to the price payable by the third party
         acquiror to the Security Trustee and be paid to the Security Trustee.
         Payment of the purchase price shall be made separately and without the
         present and future notarization procedures wherefore nothing else is to
         be stated in this or in the future deeds in that respect, and the
         Notary Public is being relieved accordingly. The Pledgor, being the
         sole owner and holder of the Share, hereby expressly declares its
         approval of the aforesaid assignment and transfer (and this approval
         shall constitute the consent to the transfer in accordance with article
         5 ("Ubertragung") of the articles of association of MC GmbH. The
         Pledgor further declares that, with the receipt of the documents as per
         paragraph 8.3, the respective third party acquiror will hold the Share
         in MC GmbH held by the Pledgor prior to the effectiveness of this
         assignment and transfer and that such acquiror shall be entered in the
         competent commercial register (at present, the Commercial Register of
         the Canton of Zurich) as owner of such Share upon notification by the
         management of MC GmbH.

9.       EXPENSES AND COSTS

9.1.     The Pledgor shall, from time to time and promptly on demand by the
         Security Trustee, reimburse to the Security Trustee all costs and
         expenses (including legal fees) on a full indemnity basis together with
         any applicable VAT incurred by the Security Trustee and any Delegate
         (provided that in relation to paragraph 9.1.1 of this clause 9, such
         costs and expenses must be properly incurred) in connection with:

9.1.1.   The execution, release and discharge of this Agreement and the Security
         created or intended to be created in respect of the Share and
         perfection of the Security

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         contemplated in this Agreement or in any such documents or forming part
         of the Security created or intended to be created in respect of the
         Share;

9.1.2.   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, the Security Trustee or any Delegate, or any
         amendment or waiver in respect of this Agreement;

9.1.3.   The foreclosure of the Share or any part of it; and

9.1.4.   The preservation and/or enforcement of the Security created or intended
         to be created in respect of the Share,

         which shall carry interest from the date of such demand until so
         reimbursed at the rate and on the basis as mentioned in Clause 18.4
         (Interest on Demands) of the Intercreditor Deed.

10.      TAXES

         The Pledgor shall pay, promptly on demand of the Security Trustee all
         stamp, registration, notarial and other similar Taxes or fees paid or
         payable by the Security Trustee in connection with any action taken or
         contemplated by or on behalf of the Security Trustee for perfecting,
         enforcing, releasing, cancelling, reassigning or resolving any doubt
         concerning, or for any other purpose in relation to this Agreement, any
         amendment thereto, any transfer and/or assignment of the rights and/or
         obligations under the same or the Security created or intended to be
         created in respect of the Share 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 the Pledgor or
         any delay by any Pledgor in paying any such Taxes or fees.

11.      MISCELLANEOUS

11.1.    During the continuation of this Agreement, the Security Trustee will at
         no time declare itself to be the beneficial owner of the Share or any
         additional pledged shares and the Security Trustee may disclose and
         deliver a copy of the present Agreement to any tax or other authority,
         if asked to do so.

11.2.    The Security Trustee may assign or transfer all or any of its rights
         and obligations under this Agreement in accordance with the
         Intercreditor Deed. The Security Trustee shall be entitled to disclose
         such information concerning the Pledgor and/or

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                                                                          - 11 -

         MC GmbH and this 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. The Pledgor hereby agrees to any person or entity
         replacing the Security Trustee as Security Trustee, subject to the
         terms of the Intercreditor Deed.

11.3.    Should one or several of the provisions of this Agreement be invalid or
         unenforceable, this shall not affect the validity and enforceability of
         the other provisions hereof. In such case, the parties will use their
         best efforts to replace the invalid or unenforceable provision or
         provisions by valid ones reflecting the meaning and intentions of this
         Agreement as closely as possible. The parties shall proceed in the same
         manner if a loophole is discovered.

11.4.    The parties hereto each acknowledge that the Security Trustee, when
         acting hereunder, shall be acting in accordance with and subject to the
         terms of the Intercreditor Deed.

11.5.    Notwithstanding any provision to the contrary contained herein, the
         parties agree that this Agreement is subject in all respects to the
         terms of the Intercreditor Deed and for the avoidance of doubt, in the
         event of any inconsistency, the provisions of the Intercreditor Deed
         shall prevail.

11.6.    No modification or amendment of this Agreement shall be binding upon
         any party hereto unless such modification or amendment is made in
         accordance with the Intercreditor Deed. Any amendment shall be in
         writing and executed on behalf of the Pledgor by a duly authorized
         officer thereof.

11.7.    No failure or delay by a party in exercising any right, power or
         privilege under this Agreement shall operate as a waiver thereof nor
         shall any single or partial exercise of any right, power or privilege
         preclude any other or further exercise thereof or the exercise of any
         other right, power or privilege.

11.8.    All communications to be made hereunder shall be made in accordance
         with the provisions of Clause 20 (Notices) of the Intercreditor Deed.

11.9.    This Agreement shall become effective on the Issue Date.

12.      GOVERNING LAW

         This Agreement shall be governed by, and construed in accordance with,
         the (domestic substantive) laws of Switzerland.

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13.      JURISDICTION

         Any and all disputes arising out of or in connection with this
         Agreement including but not limited to matters of validity, conclusion,
         binding effect, interpretation, construction, performance or
         non-performance and remedies shall be subject to the non-exclusive
         jurisdiction of the Commercial Court ("Handelsgericht") of the Canton
         of Zurich, Switzerland, venue being Zurich 1, subject to review as
         provided for by law. If there is no ordinary place of foreclosure in
         Switzerland according to the Federal Statute on Debt Collection and
         Bankruptcy (SchKG), the place of foreclosure ("Betreibungsort") shall
         be Zurich 1, which shall be the place of performance for obligations
         arising under this Agreement.

14 May 2003

Executed by:

MARCONI COMMUNICATIONS B.V., AS PLEDGOR

MARC NATER

Dr. Marc Nater with proxy

THE LAW DEBENTURE TRUST CORPORATION p.l.c., AS SECURITY TRUSTEE

MICHA BLATTMANN

Micha Blattmann with proxy

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                            NOTARIAL AUTHENTIFICATION

The undersigned Civil Law Notary of the Canton of Zug, Switzerland, Carole
Fontannaz, Attorney-at-Law, Baarerstrasse 8, CH-6301 Zug, on request of the
appearing persons:

1.       Dr. Marc Nater, Attorney-at-Law, c/o WENGER PLATTNER, Goldbach-Center,
         Seestrasse 39, CH-8700 Kusnacht ZH,

         acting not in his own name, but for and on behalf of MARCONI
         COMMUNICATIONS B.V., on the basis of a power of attorney dated 1 May
         2003, attached hereto as Annex A;

2.       Micha Blattmann, Attorney-at-Law, Bar & Karrer, Baarerstrasse 8,
         CH-6301 Zug,

         acting not in his own name, but for and on behalf of THE LAW DEBENTURE
         TRUST CORPORATION p.l.c. on the basis of a power of attorney dated 9
         May 2003 which is attached hereto as Annex B;

HEREWITH CERTIFIES ("BEURKUNDET HIERMIT OFFENTLICH"):

The present public deed - including Annexes A and B - contains the declarations
and representations of the appearing persons acting on behalf of the Parties to
the Share Pledge Agreement. It has been signed in my presence by the appearing
persons acting on behalf of the contracting Parties.

Zug, 14 May 2003                                          The Civil Law Notary:

                                                          CAROLE FONTANNAZ

                                                          (Signed and Sealed)

                                                          Carole Fontannaz

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                              OFFICIAL LEGALIZATION

The undersigned Civil Law Notary of the Canton of Zug, Micha Blattmann,
Attorney-at-law, Baarerstrasse 8, 6301 Zug, Switzerland, herewith certifies this
document to be a true copy of the Public Deed of the share pledge agreement
between Marconi Communications B.V., Hoogoorddreef 9, 1101 BA,
Amsterdam-Zuidoost, The Netherlands, and The Law Debenture Trust Corporation
p.l.c., Fifth Floor, 100 Wood Street, London EC2V 7EX, UK, dated 14 May 2003 as
presented to him.

Zug, 30 May 2003                                            The Civil Law Notary

                                                            MICHA BLATTMANN
                                                            (Signed and Sealed)

                                                            Micha Blattmann