Sykes stood since the Second World War on the stage, but only at the BBC television he developed from 1948, both as an actor and as a writer for the comedy size. From 1958 to 1965, he designed his own television series, Sykes and a ... and Sykes, and belonged to the well-known comedians of his time; often he worked with Peter Sellers, Spike Milligan, Tony Hancock and Hattie Jacques. In the film, he was consistently seen in comic roles, especially in the 1960s. Thereafter he devoted himself increasingly to stage and television. Tours have taken him to Rhodesia, Australia and Canada.
2005 his autobiography was published. It bears the title If I Do not Write it, Nobody Else Will.