A combination of the two companies would create the UK's biggest food company, with estimated annual sales of £2.5bn.
Ashurst is advising longstanding client RHM, the makers of Mr Kipling cakes and Hovis, on the friendly approach.
Corporate partner Richard Gubbins is leading Ashurst's team with competition partner Roger Finbow. The firm has been RHM's preferred counsel since summer 2005, when it advised on the disposal of Golden West Foods to East Balt Guenther Holdings prior to RHM's London flotation.
Premier instructed Weil on its bid, with UK managing partner Mike Francies leading the team. Francies also headed advice to Premier on its bid for United Biscuits (UB) in September. Premier, which owns the Branston and Ambrosia brands, bowed out of the running for UB, which eventually went to a private equity consortium comprising Blackstone and PAI for £1.6bn.
Herbert Smith and Simpson Thacher & Bartlett teamed up to advise the successful bidders in that auction. Premier is the larger of the two companies, with a market capitalisation of £1.3bn since it acquired Campbell's Soup for £460m in July. Francies and corporate partner Ian Hamilton also headed the Weil team leading the advice for Premier on that transaction.
Slaughters has won a role on the RHM bid by advising Rothschild, Premier's financial advisers. There had to be cash confirmation as part of the £1bn approach. RHM's financial advisers are Credit Suisse and Citigroup, which have not instructed any firms.