Hampton became involved in the theatre while at Oxford University. The Oxford University Dramatic Society (OUDS) performed his original play "When Did You Last See My Mother?", about adolescent homosexuality. He drew from his own experiences at Lancing. Hampton sent the work to the play agent Peggy Ramsay, who interested William Gaskill in it. The play was performed at the Royal Court Theatre in London, and soon transferred to the Comedy Theatre; in 1966, Hampton was the youngest writer in the modern era to have a play performed in the West End. Hampton's work on screenplays for the cinema also began around this time. He adapted this play for Richard Attenborough and Bryan Forbes, but a film version was never made.