The pair left JP Morgan three years ago, running the new business from offices in St James's, in London's West End. BlueCrest employs 50 people, but is secretive about its partnership structure.

The move is, of course, strictly legalistic. The new home of BlueCrest will house but a handful of employees, and Messrs. Platt, Cox, Dehadray, Dodd, Sambrook and Mmes. Braga and Kerridge ...