Allen & Overy (A&O) has been brought in to provide support to Norton Rose on the restructuring of Telewest's £5.3bn debt mountain.
Norton Rose partner Michael Ings advised the arrangers when the original debt was issued and since then has advised on all the subsequent financings.
However, it is understood that Telewest wanted to bring in another firm to provide support on US insolvency and workouts.
A consortium of banks, led by CIBC, invited five firms to pitch for the work, including A&O, Latham & Watkins and White & Case.
Clifford Chance was not asked to tender, but this is likely to be because it is advising the banks on the restructuring of NTL, which is forecast for a possible merger with Telewest at a later date.
The lead arrangers on the original financing were CIBC, Bank of New York, Toronto-Dominion and JPMorgan (now JPMorgan Chase) and Ings has been instructed in telecoms work by three of the four banks.
Telewest has not yet made its plans public, but two weeks ago it announced that it wanted to talk to its bondholders and US investor Liberty Media about a company restructuring. If the workout follows a similar structure to NTL's, where the companies issuing bonds have been put into Chapter 11, then it will require US insolvency advice.
The bondholders have so far instructed Cadwalader Wikersham & Taft, while Liberty has made a tender offer to buy bonds. As with NTL, if there is a debt for equity swap, then buying Telewest bonds would put Liberty in a position to acquire equity and therefore increase the potential for a merger with NTL, in which Liberty is also an investor.
Telewest is being advised by long-term adviser Weil Gotshal & Manges.