John Cleese
John Cleese (born 27th October 1939) played an art gallery visitor in City of Death, written by Douglas Adams. Best known for his work on Monty Python's Flying Circus (a series to which Adams also contributed), Cleese moved on from Python to star in the classic sitcom Fawlty Towers (which was in production around the time of his Doctor Who appearance), and in the 1980s established himself as an acclaimed character actor, with roles ranging from the dramatic (the western Silverado) to award-winning comic roles (such as the hit film A Fish Called Wanda and an Emmy-winning appearance on Cheers). In the 1990s he joined the James Bond film franchise as the new Q, most recently appearing in that role in Die Another Day (2002). He also appears in several of the Harry Potter films as "Nearly Headless Nick".
Although five of the six main Monty Python members have been rumoured to be considered for the role of the Doctor, Cleese remains the only one of them to actually appear on the series. Michael Palin however was namechecked in Partners in Crime.