During the production of Stanley Kubrick's 1968 film "", Davenport read the lines of HAL 9000 off-camera during the computer's dialogues with actors Keir Dullea and Gary Lockwood. However, Kubrick thought that Davenport's English accent was too distracting, and after a few weeks he dismissed him, so Canadian actor Douglas Rain was ultimately chosen for the role. Davenport took the leading role in the off-beat "Phase IV" (1974), which failed to find an audience. In 1979 he portrayed King George III in "Prince Regent".