third role, the chauffeur Charles in Miranda, Barker realised he wanted to be a comic actor. He was described as "ha[ving] the talent to be a great straight actor", but noted: "I want to make people laugh. Never mind about Hamlet. Forget Richard the Second. Give me Charley's Aunt. My mission in life was now crystal clear." He appeared in stage adaptations of Treasure Island and Red Riding Hood before getting his first leading role in The Guinea Pig as a working-class boy at a public school. When the production moved to Rhyl, Barker followed. The Manchester Repertory Company closed, as did the Rhyl company shortly after. Barker, aged 20, then spent some time as a porter at Wingfield Hospital; he became distressed through his contact with polio patients and so opted to take on the persona of "Charlie" so as not to be himself. He and a male nurse often entertained the patients with comedy routines. He found work at the Mime Theatre Company, performing mimed folk music and dance, which soon folded in Penzance. He made his way back to Oxford and then worked in Bramhall for the Famous Players. There he met actor Glenn Melvyn; the two became firm friends and Barker stated Melvyn taught him everything he "ever learned about comedy." He joined the Oxford Playhouse in 1951 and worked there for three years, appearing in plays such as He Who Gets Slapped as Polly. Peter Hall worked with Barker at Oxford and gave him his break, casting him as the Chantyman and Joe Silva in his production of Mourning Becomes Electra at the Arts Theatre in London's West End in 1955. By the time he had made it to the West End, Barker had appeared in an estimated 350 plays. Barker remained a West End actor for several years, appearing in numerous plays between 1955 and 1968. These included, in 1955, two performances each night as he played a gypsy in Listen to the Wind at the Arts Theatre and then a peasant in Summertime later in the evening. Other roles included Mr. Thwaites in Double Image in 1956 (with Olivier), Camino Real (directed by Hall) in 1957, French gangster Robertoles-Diams in Irma La Douce for two years from 1958, Lord Slingsby-Craddock in Mr. Whatnot in 1964 and Birdboot in The Real Inspector Hound in 1968. He also appeared in several Royal Court Theatre productions,