<PAGE>   1
                                                                  EXHIBIT 10.57


                                                   UNIT 1, GENESIS BUSINESS PARK
                                                                    ALBERT DRIVE
                                                                      SHEERWATER
                                                                          WOKING
                                                                 SURREY GU21 5RW




Date: 1 August 1995


                                  TELEWEST PLC
                   NON-EXECUTIVE DIRECTORS APPOINTMENT LETTER

Dear  Sir Gordon

As you are aware, it is now anticipated that the merger of TeleWest
Communications plc and SBCC Cablecomms (UK) will proceed later this year. As you
know, the merger will be effected through the formation of a new company
TeleWest plc ("the Company"), which will acquire both TeleWest Communications
plc and SBCC CableComms U.K. When that process is completed, we would very much
like you to serve as a Non-Executive Director of the Company. Of course, at that
stage there would be little point in your continuing as a Non-Executive Director
of TeleWest Communications plc. I attach a letter of resignation you could use
for that purpose, I should be grateful if you could sign that letter and return
it to Victoria Hull.

If you are willing to accept the appointment as a Non-Executive Director of the
Company, the terms which would apply to you are set out below. You will see that
they are identical to those which currently apply between you and TeleWest
Communications plc.

For confirmation, you should note that your resignation as a director of
TeleWest Communications plc and appointment as a Non-Executive Director of the
Company will take effect upon the shares of the Company being admitted to the
Official List of The London Stock Exchange.

1.   As a Non-Executive Director you will be expected to attend board meetings,
     the annual general meeting of the Company and any extra-ordinary general
     meetings of 



                                      1
<PAGE>   2

     the Company which may be called. It is anticipated that board meetings will
     be held quarterly, although on occasion it may be necessary to call board
     meetings on short notice. You will receive details of board meetings in
     advance for your diary, and an agenda will normally be circulated a few
     days before each meeting. The audit committee will be as presently
     constituted, save in respect of the participation of a representative of
     SBC and Cox instead of TCI. We should be pleased if you would continue in
     your currrent capacity on this committee.

2.   As you know, your appointment and re-appointment as a Non-Executive
     Director has to be ratified each year by the shareholders of the Company,
     as required by the Articles of Association. Subject to this, we anticipate
     your appointment will expire at the same time as your original appointment
     with TeleWest Communications plc, that is November 1997, but which may be
     renewed for a further three years if both you and the board agree.

3.   Whilst I am sure you do not need me to remind you of your responsibilities
     as a Non-Executive Director of the Company, I would wish to make clear that
     you will be under an obligation to communicate to the board any conflicts
     which may arise during the period when you serve as a Non-Executive
     Director. The board will then be able to decide what (if any) action needs
     to be taken about that. In addition, it is of great importance that you do
     not disclose to anybody outside the Company or any of its subsidiaries any
     trade secrets or other confidential information concerning the Company or
     any of its subsidiaries which may come to your knowledge by virtue of your
     position as a Non-Executive Director. During your appointment as a
     Non-Executive Director the board would expect you to refrain from accepting
     appointments (whether as agent, employee or consultant) with any company or
     firm engaged in a business competing with or similar to that of the Company
     or any of its subsidiaries.

4.   We are also obliged to require that, upon the Company's shares being
     admitted to listing on the London Stock Exchange, you comply with the
     "Model Code" issued by the International Stock Exchange of Great Britain
     and the Republic or Ireland in relation to dealings in shares by you and
     anybody connected with you. We anticipate that the Company will adopt its
     own share dealing code in similar terms to the "Model Code" of the London
     Stock Exchange shortly.

5.   The Rules of the London Stock Exchange also require us to submit to the
     Securities and Futures Authority Limited a "declaration of a directors
     business activities" in the form set out in Schedule 7 to the Listing Rules
     of the London Stock Exchange. By accepting this appointment you undertake
     to complete such a declaration and authorise the Company to submit it to
     the Securities and Futures Authority Limited. In addition, you agree that
     you will notify the Company as soon as practicable of any changes to the
     details set out in the declaration.

6.   For serving as a Non-Executive Director of the Company, you will be
     entitled to receive a fee, presently (pound) 20,000 per annum payable
     quarterly in arrears. The level of



                                       2
<PAGE>   3

     Non-Executive Directors fees is reviewed annually. You also receive (pound)
     1,000 for every board meeting of the Company you attend. In addition, the
     Company will of course reimburse you for any expenses you might incur in
     the performance of your duties, these can include reasonable travel and
     other identical expenses which you might incur. I would wish to make clear
     that such expenses may include legal fees if circumstances should arise in
     which it is necessary for you to seek separate legal advice about the
     performance of your duties. This could, of course, be a little awkward and
     in that situation you might find it helpful to discuss the issue either
     with me or one of your Non-Executive colleagues in advance should you think
     it appropriate.

I hope that you find the above terms are in order. I should be grateful if you
will confirm your agreement to them by signing and returning to me the enclosed
counter part of this letter.

Yours sincerely


/s/ Alan Michels
-----------------------
ALAN MICHELS
CHIEF EXECUTIVE OFFICER






                                       3