Slaughter and May has advised Standard Life Assurance on the £6.7bn reinsurance of some of its annuity liabilities to Canada Life International Re – thought to be the largest deal of its kind in the UK to date.

The deal closed on 14 February and the Slaughters team was led by corporate partner Craig Cleaver and tax partner Graham Earles. The firm has acted for Standard Life since it won a competitive tender to advise the insurer on its demutualisation in 2004 and subsequent stock market flotation.

Herbert Smith has taken the lead role for longstanding client Canada Life. The firm fielded a team led by corporate partner Geoffrey Maddock, assisted by lawyers including finance partner Laurence Elliott.

The firm has previously advised on deals including Canada Life's £2.2bn acquisition of a book of annuities from Resolution Life.

The agreement, which came after four months of negotiations, covers more than half of the insurance company's £12bn UK annuity liabilities N significantly reducing its exposure to the UK market.

Cleaver told Legal Week he believed there would be increasing numbers of these transactions in the future, adding: "We have been heavily involved in this sector and this deal only reflects the continuing trend to hedge longevity risks."

Standard Life has seen its payment responsibilities to policyholders significantly increase as the life expectancy of the UK's population has grown.

Maddock said: "This is the biggest example of a UK insurance company offloading risks of pensioners living longer than expected to a company with a very different appetite. This is very significant for Standard Life."