Allen & Overy (A&O), Simpson Thacher & Bartlett, Wachtell Lipton Rosen & Katz and Gibson Dunn & Crutcher have snared the key advisory roles on the £5.6bn takeover of UK pharmacy chain Alliance Boots by US drugs giant Walgreens.

Walgreens will take full control of Boots in early 2015, acquiring the 55% share in the company it did not already own.