Document:

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                                                                  Exhibit 10.25
                                 PROMISSORY NOTE

L316,375.62 [equal to $500,000]                  Effective date: April 1, 2000

         FOR VALUE RECEIVED, Bob Koenig (the "MAKER") does hereby promise to pay
to FirstMark Communications Europe SA ("FMCE") or its assigns (the holder of
this promissory Note being referred to as the "HOLDER"), the principal sum of
$500,000.

         1. PAYMENT. Subject to Section 2 below, all sums payable hereunder
shall be collected from the Maker by the Holder by means of a check or money
order made payable to the Holder at [ ] or at such other place or places as the
Holder may direct from time to time. The principal balance of this Promissory
Note shall be paid (i) in five annual payments to the Holder in the amount of
$100,000 (the "INSTALLMENT PAYMENT"), with the first Installment Payment due and
payable on April [ ], 2001, and each of the next four (4) Installment Payments
due and payable on each succeeding April [ ] (each payment date referred to
herein as the "INSTALLMENT DATE"). Notwithstanding the foregoing, all amounts
shall be due and payable immediately in the event that the Employee is
terminated by FirstMark Communications Europe Services Limited (or its
successor) for cause or terminates his employment other than for good reason,
or, subject to Section 2 below, one year after termination of employment for any
other reason.

         2. FORGIVENESS. If, as of an Installment Date, the Maker continues to
be Chief Financial Officer of FirstMark Communications Europe Services Limited
(or its successor), the Holder shall forgive the Installment Payment due and
payable as of such Installment Date, and FMCE shall treat the forgiveness as
compensation to Mr. Samples; provided, however, that as a condition to such
forgiveness, the Maker shall make arrangements that are satisfactory to the
directors of FMCE in their sole discretion with respect to the Maker's payment
to FMCE of the amount that is necessary to be withheld (if any) in accordance
with applicable withholding requirements.

         3. INTEREST. The outstanding principal balance of this Promissory Note
shall bear interest at a rate per annum equal to __% [equal to] compounded
annually (the "RATE").

         4. PREPAYMENT. This Promissory Note is subject to prepayment at any
time or from time to time at the option of the Maker, either in whole or in
part, without premium or penalty.

         5. DELINQUENCY RATE OF INTEREST. All past due and delinquent sums
hereunder, both principal and interest, shall earn interest until such sums have
been paid at the rate that is the lesser of (a) 12% or (b) the maximum rate of
interest permitted

<PAGE>

by applicable law. Interest shall be computed on the basis of a 365 day year for
the actual number of days elapsed.

         6. COLLECTION EXPENSES. If there is a default under this Promissory
Note and this Promissory Note is placed in the hands of an attorney for
collection, or in the event that this Promissory Note is collected in whole or
in part by suit or through probate or bankruptcy proceedings, or other legal
proceedings of any kind, the Maker agrees to pay, in addition to all the sums
payable hereunder, the Holder's reasonable expenses of collection, including,
without limitation, reasonable attorneys' fees and disbursements, whether or not
suit is brought and through all appeals.

         7. GENERAL PROVISIONS. Time shall be of the essence with respect to the
terms of this Promissory Note. This Promissory Note cannot be changed or
modified orally.

         8. GOVERNING LAW. This Promissory Note shall be construed in accordance
with and governed by English law.

         EXECUTED this 1st day of April, 2000, to be effective as of the date
first set forth above.

                                                     MAKER:

                                                     /s/ Bob Koenig
                                                     -------------------------
                                                     BOB KOENIG

                                      -2-<PAGE>
                                                                 Exhibit 10.26

               [Letterhead of FirstMark Communications Europe SCA]

                                              February 17, 1999

Mr. Michael Taylor
109 Hallowell Road
Northwood
Middlesex
HA6 1DY
United Kingdom

Re: Terms and Conditions of Employment

Dear Michael:

The following sets out the terms and conditions of your employment with the
FirstMark Communications Europe:

1.    Salary: 110,000 UK pounds sterling per year paid monthly and subject to
      annual review.

2.    Bonus: 25,000 UK pounds sterling per year subject to annual review.

3.    Stock: Initial grant of 75,000 share options at nominal price with further
      grants to follow at company's discretion.

4.    Notice of termination of employment: 3 monthly (company to employee and
      employee to company).

5.    Holiday entitlement: 25 days

6.    Other benefits: company policy process to be established.

7.    Title: Vice President and General Counsel

                                                      Very truly yours,

                                                      /s/ Michael J. Price

                                                      Michael J. Price
                                                      Co-Chief Executive Officer

Agreed and Accepted:
Michael J. Taylor

/s/ Michael J. Taylor
---------------------
<PAGE>

                              Dated March 19, 1999

                       FIRSTMARK COMMUNICATIONS EUROPE SCA

                                      -and-

                                 MICHAEL TAYLOR

                             CONTRACT OF EMPLOYMENT
<PAGE>

THIS AGREEMENT is made on the 19th day of April 1999

BETWEEN

(1)   FIRSTMARK COMMUNICATIONS EUROPE SCA a company incorporated in Luxembourg
      and having its registered address at 6, Rue Jean Monnet, L-2180 Luxembourg
      ("the Company"); and

(2)   MICHAEL TAYLOR of 109 Hallowell Road, Northwood, Middlesex, HA6 1DY,
      United Kingdom ("the Employee").

NOW IT IS HEREBY AGREED that the Company shall employ the Employee and the
Employee shall serve the Company as Vice President and General Counsel, or in
such other capacity as may from time to time be mutually agreed, upon and
subject to the following terms and conditions:

1     Interpretation

1.1   In this Agreement unless the context otherwise admits the following
      expressions shall have the meanings given to them as follows:

      "the Directors" means those members of the Board of Directors for the time
      being of the Company and "subsidiary" and "holding company" means a
      subsidiary or holding company as defined by Section 736 and 736A of the
      Companies Act 1985 for the time being of the Company (and "subsidiaries"
      and "holding companies" shall be construed accordingly);

      "associated company" means any holding company or subsidiary of the
      Company or any other subsidiary of such holding company;

1.2   Any reference to a statutory provision shall be deemed to include a
      reference to any statutory modification or re-enactment of the same.

2     Commencement and Duration

2.1   The Employee's employment with the Company shall commence on the date
      hereof. No previous employment of the Employee shall be treated as being
      continuous with the Employee's employment with the Company.

2.2   Subject to termination as hereinafter provided, the employment of the
      Employee shall continue from year to year provided that the Company may
      terminate the employment at any time by giving to the Employee three
      months' written notice to terminate this Agreement and the Employee may
      terminate his employment at any time by giving to the Company three
      months' written notice to terminate this Agreement.
<PAGE>

2.3   The Employee warrants to the Company that he is not restricted in any way
      from commencing and continuing employment with the Company on and after
      the date hereof. The Employee shall indemnify and keep indemnified the
      Company against any and all damages, losses, costs and expenses (including
      the costs of any legal proceedings to which the Company may be party to)
      arising from the Employee being in breach of the warranty contained in
      this sub-clause.

3     Remuneration

3.1   The Employee shall be entitled to a fixed salary at the rate of
      (pound)110,000 (one hundred and ten thousand UK pounds sterling) per annum
      (which shall accrue from day to day) payable by equal monthly instalments
      in arrears on the last working day of every month.

3.2   The first of such payments shall be made on the last day of the month in
      which the Employee's employment commences and shall be a pro rata amount
      in respect of the period from the date hereof to the last day of such
      month.

3.3   The Employee's salary shall be reviewed by the Company no later than, and
      with effect from, each anniversary of the Employee's employment with the
      Company, such review to be in line with the Company's then current policy
      on remuneration review.

3.4   The Company shall be entitled to deduct from the Employee's salary or from
      any other payments due to the Employee any amount which the Company is
      required by law to deduct (including without limitation PAYE or national
      insurance).

4     Bonus

      The Company shall pay to the Employee a bonus of (pound)25,000 (twenty
      five thousand UK pounds sterling) on the first anniversary of the
      Employee's employment with the Company. Thereafter, the Company shall
      continue to pay to the Employee an annual bonus in line with the Company's
      policy for the payment of bonuses, such amount to be subject to review.

5     Stock

5.1   The Directors of the Company shall, with effect from the date of this
      Agreement, grant to the Employee an option to subscribe for 75,000
      (seventy five thousand) Company common stock of US$ each at a subscription
      price per ordinary share of US$0.01. The option is exercisable in
      accordance with the terms of scheme rules to be established by the Company
      ("Scheme Rules"). It shall be the responsibility of the Employee to put in
      place Scheme Rules acceptable to the Directors of the Company.

5.2   The Directors of the Company shall at their discretion, and in accordance
      with the Scheme Rules, from time to time grant to the Employee stock
      options in addition to those referred to in sub-clause 5.1.
<PAGE>

5.3   With respect to the grant of stock options, the Employee shall comply, and
      shall continue to comply with, all the requirements of applicable laws and
      regulations which are relevant to the grant of stock options to the
      Employee.

5.4   Sock options granted to the Employee under sub-clause 5.1 shall vest 25
      (twenty five) per cent on the first anniversary of this Agreement and
      thereafter at the rate of 25 (twenty five) per cent per annum. All
      subsequent grants of stock options shall vest in accordance with the
      Scheme Rules at the rate of 25 (twenty five) per cent per annum over a
      period of four years commencing from the date of grant. Stock options will
      vest 100 (one hundred) per cent if the Company is acquired by a third
      party.

6     Devotion of Whole time to the Company

6.1   During his employment with the Company the Employee shall, unless
      prevented by ill- health or holiday:

6.1.1 perform such reasonable duties and exercise such powers, authorities and
      directions as the Directors may from time to time reasonably assign or
      vest in him in conjunction with the business of the Company and any one or
      more of the Company's subsidiaries or associated companies;

6.1.2 attend at meetings of the senior management of the Company;

6.1.3 devote his whole time and attention during normal working hours to the
      business of the Company and such other time as may be necessary for the
      performance of his duties hereunder;

6.1.4 do all in his power to promote, develop and extend the business of the
      Company;

6.1.5 conform to and comply with the reasonable directions and regulations made
      by the Directors or any other properly authorised person;

6.1.6 not, without the previous consent in writing of a Director engage or be
      concerned or interested in any other business of a similar nature to or
      competitive with that carried on by the Company or any of its subsidiaries
      or associated companies

PROVIDED always that nothing in this clause 6 shall preclude the Employee from
holding, or being otherwise interested in any shares or other securities of any
company which is for the time being quoted on any recognised stock exchange, so
long as the interest of the Employee therein does not without the written
consent of the Directors extend to more than 3 (three) per cent of the aggregate
amount of the quoted securities of any class in respect of any company.

6.2   During the employment of the Employee with the Company:
<PAGE>

6.2.1 the Employee may be required, on a temporary basis, to work at such place
      or places in the United Kingdom or overseas as may be determined by the
      Company from time to time and undertake such travel overseas as may be
      reasonably required; and

6.2.2 the Employee shall report to Michael J. Price, Co-CEO and Director of the
      Company (or whosoever shall be the CEO of the Company for the time being).

7     Benefits

7.1   The Employee shall be responsible for putting in place a Company benefits
      programme acceptable to the Directors. Such benefits programme shall
      include, but not necessarily be limited to, health care, disability
      insurance, life cover and a contributory pension scheme.

7.2   In respect of the benefits programme referred to in sub-clause 7.1, the
      Company shall pay the premiums in respect of private medical and dental
      expenses insurance effected on behalf of the Employee and the Employee's
      spouse as in accordance with Company policy. The Employee shall during his
      employment with the Company be a member of a death-in-service and
      disability benefit scheme maintained by the Company in respect of the
      Employee (or any scheme set up in its place).

8     Expenses

      The Company shall pay or procure to be paid to the Employee all reasonable
      travel, hotel and other out-of pocket expenses wholly exclusively and
      necessarily incurred by the Employee in the proper performance of his
      duties under this Agreement. Any such payment shall be subject to
      providing the Company with satisfactory receipts or other evidence of
      actual payment of said expenses.

9     Absence through illness

9.1   In the case of illness of the Employee or other cause incapacitating him
      from properly performing his duties, the Employee shall, subject to clause
      9.2, and to the production of such satisfactory medical evidence as the
      Company may reasonably require, continue to be paid his full salary during
      such absence.

9.2   If such absence shall aggregate 16 (sixteen) weeks in any 52 (fifty two)
      consecutive weeks, the Company may terminate the employment of the
      Employee forthwith by written notice given within 28 (twenty eight) days
      of the end of the last 16 (sixteen) weeks. On termination pursuant to this
      clause 9.2, the Company shall pay to the Employee a sum equal to three
      months salary from the date of such termination.

9.3   The amounts payable by the Company to the Employee under this clause 9
      will be reduced by the amount of any statutory sick pay payable to the
      Employee.
<PAGE>

10    Holidays

      The Employee shall (in addition to the usual Bank Holidays and public
      holidays) be entitled to 25 (twenty five) days paid holiday in each
      calendar year to be taken at a time or times mutually agreed with the
      Company.

11    Confidentiality and Non-Disclosure

11.1  The Employee shall not either during his employment hereunder or at any
      time after its termination:

11.2.1 disclose to any person or persons (except those authorised by the Company
to know);

11.2.2 use for his own purpose or for any purposes other than those of the
Company; or

11.2.3 through any failure to exercise all due care and diligence cause any
unauthorised disclosure of any private, confidential or secret information of
the Company (including lists or details of customers of the Company or relating
to the working of any process or invention carried on or used by the Company or
any invention of the Company) or which he has obtained by virtue of his
appointment or in respect of which the Company is bound by an obligation of
confidence to a third party. These restrictions shall cease to apply to
information or knowledge which may (otherwise than through default of the
Employee) become available to the public generally.

11.3  The provisions of this clause 11 shall apply equally in relation to the
      private, confidential or secret information of any subsidiary or
      associated company of the Company which the Employee may have received or
      obtained during his appointment and the Employee shall upon request enter
      into an enforceable agreement with any such company to the like effect.

11.4  All notes, memoranda, records and writing (in whatever format) made by the
      Employee relating to the business of the Company or any subsidiary or
      associated company of the Company shall be and remain the property of the
      Company such subsidiary or associated company to whose business they
      relate and shall be delivered by him to the company to which they belong
      forthwith upon request.

12    Summary Termination

12.1  The employment of the Employee hereunder may be terminated forthwith by
      the Company without payment in lieu of notice if the Employee:

12.2  is guilty of any gross misconduct in connection with or affecting the
      business of the Company or any of its subsidiaries or associated
      companies; or
<PAGE>

12.3  is in material breach of any of the provisions of this Agreement unless
      the breach is capable of remedy and is not remedied within 7 (seven) days
      of notice by the Company requiring remedy; or

12.4  commits an act of bankruptcy or becomes insolvent or suffers any similar
      or analogous action on account of debt.

13    Reconstruction

      If the employment of the Employee is terminated by reason of the
      liquidation of the Company for the purpose of reconstruction or
      amalgamation, the Employee shall be offered employment with any concern or
      undertaking resulting from such reconstruction or amalgamation on terms
      and conditions no less favourable than the terms of this Agreement. The
      Employee shall in such circumstances have no claim against the Company in
      respect of the termination of his employment.

14    Effect of Termination

14.1  The termination of the Employee's employment in accordance with the terms
      of this Agreement howsoever occasioned shall not prejudice any claim which
      either party may have against the other in respect of any antecedent
      breach of any provision of this Agreement, nor shall it prejudice the
      continuance in force of any provision which is, expressly or by
      implication, intended to come into, or continue in force on or after such
      termination.

14.2  Upon the termination for whatever reason of the Employee's employment
      hereunder, the Employee shall thereafter, upon the request of the Company:

14.3  Resign without claim for compensation from office of the Company and such
      other offices held by him in the Company or any of its subsidiaries or
      associated companies as may be so requested. In the event of the
      Employee's failure to do so forthwith upon request, the Company is hereby
      irrevocably authorised to appoint some person in his name and on his
      behalf sign and deliver such resignation or resignations to the Company
      and to each subsidiary or associated company of the Company of which the
      Employee is at the material time an officer; and

14.4  Hand over to the Company or as it may direct and without retaining copies
      of the same all documents, books, correspondence and other papers of
      whatsoever nature relating to the business of the Company and any of its
      subsidiaries or associated companies which may then be or ought to be in
      his possession.

15    Pay in Lieu of Notice

      On serving notice for any reason to terminate this Agreement the Company
      shall instead of giving the Employee the appropriate period of notice be
      entitled (at its sole discretion) to pay to the Employee his salary and
      full
<PAGE>

      contractual benefits (at the rate then current) for the appropriate period
      of notice of such termination.

16    Leave of Absence

16.1  On serving notice for any reason to terminate this Agreement the Company
      may (at its sole discretion) require the Executive to take paid leave of
      absence equal in length of time to the Employee's entitlement to notice of
      such termination.

16.2  Whilst on such leave of absence the Employee shall not, without the
      Company's prior written consent, or at the Company's request, contact any
      Company employee, customer or supplier of the Company.

17    Grievance and Disciplinary Procedures

      There is no formal disciplinary procedure applicable to this Agreement.
      Should the Employee have a grievance this should be discussed with the CEO
      for the time being in place.

18    Severability

      Each and every provision in this Agreement shall be read as a separate and
      distinct undertaking and the invalidity, legality or unenforceability of
      any part of this Agreement shall not affect the validity, legality or
      enforceability of the remainder.

19    Waiver

      No waiver by the Company or the Employee of any of their respective rights
      hereunder shall be deemed a continuing waiver of any such rights
      hereunder.

20    Assignment

      The Company shall be entitled to assign its rights under this Agreement to
      any of its subsidiaries or associated companies by whom the Employee shall
      for the time being be employed or on behalf of which he shall at any time
      work and the Employee agrees to accept any such assignment.

21    Notices

21.1  Any notice to be given under this Agreement shall be sufficiently served:

21.2  In the case of the Employee by being delivered either personally to him or
      sent by registered post or recorded delivery to his usual or last known
      residential address in the United Kingdom; and

21.3  In the case of the Company by being personally delivered at or sent by
      registered post or recorded delivery addresses to its registered office.
<PAGE>

21.4  Any such notice on sub-clauses 21.2 and 21.3 shall be deemed served on the
      second day following that on which it was posted.

22    Governing Law

      This Agreement shall be subject to English law and the parties hereby
      agree to and submit to the non-exclusive jurisdiction of the English
      courts.

23    Previous Agreements

23.1  This Agreement supersedes all existing agreements, arrangements,
      contracts, representations and understandings (oral and written) for the
      employment of the Employee by the Company.

23.2  The Employee hereby acknowledges that he has no outstanding claims of any
      kind against the Company.

24    Post-Termination Restrictions

24.1  The Employee shall not during the course of his employment with the
      Company, and for a period of 12 (twelve) months after termination of his
      employment with the Company, be engaged as a director, officer, employee
      or consultant in any concern which is or shall be wholly or partly in
      competition with any aspect of the Company's broadband wireless local loop
      business.

24.2  The Employee agrees that he shall not, for a period of 12 (twelve) months
      after termination of his employment with the Company, solicit or entice
      away or seek to entice away from the employment of the Company any person
      who is or was at the date of the Employee's termination of employment
      employed by the Company in a senior managerial, technical, supervisory,
      sales or marketing capacity and with whom the Employee dealt in the course
      of his duties in the 12 (twelve) months prior to termination of
      employment.

24.3  The Employee agrees that he shall not, for a period of 12 (twelve) months
      after termination of his employment with the Company, solicit any business
      from any person who during the 12 (twelve) months prior to termination of
      the Employee's employment was a customer of the Company and with whom the
      Employee has had personal dealings.

25.   Data Protection

      The Employee acknowledges and agrees that the Company is permitted to hold
      personal information concerning the Employee and that the Company may make
      use of such information in the course of the Company's normal business
      activities. The Employee further acknowledges and agrees that the Company
      may disclose such information to its associated companies and certain
      third parties in such circumstances where disclosure is necessary to
      ensure the proper conduct of the Company's business or the business of any
      of its associated companies. Personal information as referred to in this
      clause 25 may be held, used or disclosed as aforesaid in any medium
      whatsoever.
<PAGE>

26.   Intellectual Property

      The Employee shall disclose promptly to the Company any invention or
      intellectual property discovered or created by the Employee during the
      period of his employment with the Company, insofar as any discovery or
      creation relates to the business of the Company or the business of any
      associated company, and any such invention or other intellectual property
      so created shall (subject to the Patents Act 1977) belong to and be the
      absolute property of the Company. The Employee shall, whether during or
      after termination of his employment (howsoever arising) do all such
      things, execute all such documents and take any action required by the
      Company (at the Company's cost) to apply for protection in respect of any
      invention or other intellectual property and to vest the same in the
      Company or in any associated company.

AS WITNESS the hands of the parties hereto the day and year first above written

Signed by                     /s/
For and on behalf of          --------------------------
FirstMark Communications Europe SCA
In the presence of

Signed by Michael Taylor      /s/ Michael Taylor
In the presence of            ---------------------------

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