Freshfields and Linklaters & Alliance are battling to finalise Lloyds TSB's #7bn acquisition of Scottish Widows.
The sale of the Edinburgh-based life assurer, advised by Freshfields, to Lloyds TSB, represented by Linklaters, will create the second largest life, pensions and unit trust provider in the UK.
But although the sale has been agreed, Scottish Widows' status as a mutual company will prolong the closure of the deal.
Freshfields and Maclay Murray & Spens, which is advising Scottish Widows on local law, still need to get clearance from the Scottish Court of Session for the demutualisation of the life assurer.
In the autumn a circular, or scheme, document will be handed over to all Scottish Widows members, after which the life assurer must obtain a final court order on the demutualisation.
Outlining the details of the circular, Linklaters corporate partner Donald Williams, who is working on the deal with a core team of nine lawyers, says: "There will be a flat rate of #500 for everyone who is a member of Scottish Widows and a variable element which has yet to be formulated.
"The scheme itself is quite complicated - as are all these schemes when insurance companies demutualise."
Williams says Lloyds TSB will continue to use the Scottish Widows brand for the independent financial advice market and the combined business will remain in Edinburgh.
Freshfields corporate partner Philip Richards is heading the firm's eight-strong team on the deal.