The 1,800-lawyer London law firm Clyde & Co. will merge with the 18-lawyer Miami insurance defense firm Thornton, Davis & Fein on July 1 to create its sixth U.S. office.

“Miami was a leading city in the United States where we wanted to have a presence for awhile,” Michael Knoerzer, managing partner of Clyde’s New York office, said Wednesday. “We thought this was a perfect fit for us. We fully expect substantial growth commensurate with the vitality and importance of that city.”