Wansbroughs Willey Hargrave merged with Beachcroft Stanleys this week to create a 122-partner national firm, specialising in commercial, healthcare and insurance.
Beachcroft Wansbroughs, as the new firm is called, is the result of 18 months of merger negotiations.
Wansbroughs completed its first foray into national expansion after taking over Manchester insurance firm Vaudreys in September.
As a result of the merger, Wansbroughs' head office will shift from Bristol to London, where Beachcrofts' new offices are located. The new firm will have 500 professional staff and a total of 1,100 employees.
Robert Heslett, senior partner at Wansbroughs who will become managing partner under the merged operation, said that there would be no staff cuts after the merger is completed on 1 May 1999.
Heslett said the merger with Vaudreys was: "All part of a plan between the three companies to complete the national network before dealing with London."
Beachcroft Stanleys' senior partner Lord Hunt of Wirral will be a senior partner of the newly merged firm.
He said that the new firm plans to expand a network across Europe and added that the tripartite merger was established to balance the firms core areas of law including commercial, healthcare and insurance.
Mike Tinker, partner and head of the Manchester Insurance group at Dibb Lupton Alsop, said: "Geographically the merger makes sense. The insurers themselves are consolidating and law firms have to have a national presence."