Cook appeared at the first three fundraising galas staged by humorists John Cleese and Martin Lewis on behalf of Amnesty International. The benefits were dubbed "The Secret Policeman's Balls", though it wasn't until the third show in 1979 that the title was used. He performed on all three nights of the first show in April 1976, "A Poke in the Eye (With a Sharp Stick)", as an individual performer and as a member of the cast of "Beyond the Fringe", which reunited for the first time since the 1960s. He also appeared in a Monty Python sketch, taking the place of Eric Idle. Cook was on the cast album of the show and in the film, "Pleasure at Her Majesty's". He was in the second Amnesty gala in May 1977, "An Evening Without Sir Bernard Miles". It was retitled "The Mermaid Frolics" for the cast album and TV special. Cook performed monologues and skits with Terry Jones.