Ronald Harwood based his play "The Dresser" (and this film's subsequent screenplay) and the biography "Sir Donald Wolfit CBE: His life and work in the Unfashionable Theatre" on his experiences as an actor and dresser for renowned Shakespearian actor Donald Wolfit and his Shakespeare Company. Harwood was Wolfit's dresser between 1953 and 1958.
One of the critic's names on a quote on the theater foyer reviews board is "R. Harwood" of the fictitious 'Portsmouth and Gosport Express'. The name is a reference to Ronald Harwood, the film's screenwriter, source playwright and also one of the film's producers.
After Sir and Norman leave the marketplace, they're passed by a Routemaster bus. These buses were first used in London in 1954, and weren't used outside London until the 1970's.