When Simpson died aged 95 in 2017, The Guardian wrote that he was "at his most prolific as the creator of incidental music for Doctor Who in the 1960s and 1970s, contributing to 62 stories over almost 300 episodes – more than any other composer.
He also appeared on screen as a music hall conductor in the Fourth Doctor story The Talons of Weng-Chiang (1977) at the invitation of Philip Hinchcliffe, who was the producer at the time.
Simpson composed the theme tune to the ITV-based Thames Television science fiction series The Tomorrow People (1973–1979).
[1] The show involves a group of teenagers with psychic, emotional and other paranormal powers to use their special gifts to battle evil spirits.
Set in a fictional spaceship Liberator, the crew consisted of Roj Blake, Jenna Stannis, Kerr Avon, Vila Restal, Olag Gan, Cally, Dayna Mellanby, Del Tarrant and Soolin as well as the supercomputers Zen, Orac and Slave and the villains Travis and Servalan.