Hancock worked in repertory during the 1950s and made her West End debut in 1958, replacing Joan Sims in the play "Breath of Spring". She then appeared in Joan Littlewood's Theatre Workshop production of "Make Me An Offer" in 1959, and her other early West End appearances included Peter Cook's revue "One Over the Eight" with Kenneth Williams in 1961, and starring in "Rattle of a Simple Man" in 1962. She recalled that in "One over the Eight" she had been egged on by Irving Davies's exhortation as dance captain, "Eyes, teeth, and tits, darlings – and sparkle, sparkle, sparkle!"