Slaughter and May, Lovells and Allen & Overy (A&O) have won lead advisory roles on a £1bn bulk annuity deal between Cable & Wireless and Prudential, thought to be the biggest of its kind in the UK to date.

The deal saw the trustees of the Cable & Wireless Superannuation Fund agree to the £1bn buy-in of an insurance policy for its pensioner liabilities with Prudential.

Lovells advised the scheme's trustees, fielding a team led by pensions partner Stephen Ito with support from business restructuring partner Joe Bannister and financial institutions partner Dominic Hill.

Lovells has traditionally advised Prudential on this type of transaction but on this occasion the firm had already chosen to advise Cable & Wireless trustees as the company is also a longstanding client.

Instead, Prudential turned to Slaughter and May, where pensions and employment partner Philip Bennett headed the team. He was assisted by corporate finance partner Oliver Wareham, capital markets partner Guy O'Keefe and financial regulation partner Jan Putnis.

Prudential is an established client of the firm, but this is the first transaction of this kind on which Slaughters has advised.

A&O acted for Cable & Wireless with pensions partner Dana Burstow leading the team.

The annuity policy removes all risks relating to the pensioner element of the fund. Cable & Wireless has also pledged £10m in cash to the fund.

Bennett told Legal Week: "This one is the largest of its type so far this year, suggesting that the market is right for this kind of thing."

Ito added: "To breach the £1bn landmark for such a deal is significant and I suspect this will not be the last transaction of this type in 2008."