His closest friend in later life was the broadcaster David Jacobs..
His experience of serving in the British Navy during the Second World War inspired him to conceive the popular BBC radio comedy "Navy Lark, The". He was a star of the series for many years and provided the voices for many of the diverse characters.
His favorite aliens in "Doctor Who" (1963) were the Draconians from the 1973 story "Frontier in Space". In particular, he liked the quality of the half-masks that were designed for them, which allowed for more expressive performances from the actors than was sometimes able to the case.
His final screen appearance was in a "Doctor Who" (1963)-inspired advertisement for Vodaphone in 1996, shot a week before his death.
Jon was considered for the role of Captain Mainwaring in the BBC series "Dad's Army" (1968), which eventually went to Arthur Lowe. He claimed that he refused the part as he was working on Broadway at the time, and didn't know what he was being offered back home.
Knew Laurence Olivier personally when he was a young man.
Known as a comedy actor until he was cast in a dramatic and action role as the third Doctor in "Doctor Who" (1963).
Like Patrick Troughton, his predecessor as the Doctor, he died of a heart attack while visiting the United States.
Of the 24 "Doctor Who" (1963) stories he starred in, he named "Doctor Who: The Dæmons: Episode One (#8.21)" (1971) as his favorite.
Played "Lycus" in the original stage production of "Funny Thing Happened on the Way to the Forum, A". The film role was given to Phil Silvers since he had greater name-recognition internationally.
The 60 year old actor added pop star to his repertoire in 1980 when 'Worzel's Song' reached the top 33 in the UK and stayed in the chart for seven weeks.
Was a founder member, along with his brother Michael, of The Waistcoat Club (of which he had a large collection, some dating back 300 years) which was set up in 1953 to counter the drabness of mens' dress. Another future Doctor Who, Peter Cushing, was a fellow member.
Was a friend of Stephen Ward, a key figure in the John Profumo political scandal in the UK in the early 1960s.
Was a life long fan of cartoons.
Was delighted when his wife passed him the message that he had been invited to appear in "the new Columbus film", and that the script was being sent over. He would wryly recall that his hopes of working with Gérard Depardieu in 1492: Conquest of Paradise (1992) were quickly dashed when he received the script of Carry on Columbus (1992).
Was originally meant to star in The Baby and the Battleship (1956) with George Cole, but was replaced when Cole walked out.
Was the original choice for the role of Elliot Hoover in Audrey Rose (1977).
Was the producers' second choice to play Dr Who. At the time, their first choice was Ron Moody.
Was well-known for his role in the long-lived BBC Radio comedy series "The Navy Lark", where he played the role of Chief Petty Officer Pertwee (plus Vice-Admiral "Burbly" Burwasher, Commander Weatherby and The Master) from 1959 to 1977.