Hampstead was where Cook unwound, but the West End was where he dazzled. The Fortune Theatre, on Russell Street, is where he first appeared in Beyond the Fringe. At the Cambridge Theatre, on Earlham Street, he appeared in 1972 with Dudley Moore in Behind the Fridge. At Her Majesty's Theatre, on Haymarket, Cook was the linchpin of the historic Amnesty International fundraiser, The Secret Policeman's Ball, in 1979. The cast included Rowan Atkinson, Billy Connolly and most of the Monty Python team, but Cook stole the show with his wicked send-up of Mr Justice Cantley's summing up in the Jeremy Thorpe trial ("you are now to retire - as indeed should I - carefully to consider your verdict of Not Guilty").