Upon leaving school he worked as a clerk[2] at a corn merchant's in Ipswich before finding employment in London as a commercial traveller for the Sanitas Disinfectant Company.

In September 1939, at the start of the Second World War, Mills enlisted in the British Army, joining the Royal Engineers.

[5] Mills took an early interest in acting, making his professional début at the London Hippodrome in The Five O'Clock Girl in 1929.

Mills then got a job with a theatrical company that toured India, China and the Far East performing a number of plays.

Noël Coward saw him appear in a production of Journey's End in Singapore and wrote Mills a letter of introduction to use back in London.

He was in a series of quota quickies: The River Wolves (1934); Those Were the Days (1934), the first film of Will Hay; The Lash (1934); Blind Justice (1934); Doctor's Orders (1934); and Car of Dreams (1935).

He appeared as Colley in the hugely popular 1939 film version of Goodbye, Mr Chips, opposite Robert Donat.

Mills went back to supporting Will Hay in The Black Sheep of Whitehall (1942) and he was one of many names in the war film, The Big Blockade (1942).

Mills had another good support role in The Young Mr. Pitt (1942) playing William Wilberforce opposite Robert Donat.

[7] Mills's climb to stardom began when he had the lead role in We Dive at Dawn (1943), a film directed by Asquith about submariners.

Mills played a pilot in The Way to the Stars (1945), directed by Asquith from a script by Terence Rattigan, and another big hit in Britain.

It was the third biggest hit at the British box office that year and Mills was voted the sixth most popular star.

Mills played a supporting role in a movie for MGM, The End of the Affair (1955), with Deborah Kerr and Van Johnson.

More liked in Britain was another war story, Above Us the Waves (1955); this was the sixth-most-popular film at the British box office that year, and it helped Mills become the fifth-most-popular star in the country.

[19] In the 1959 crime drama Tiger Bay, directed by Thompson, Mills played a police detective investigating a murder that a young girl has witnessed.

Disney also offered John Mills the lead in the adventure film Swiss Family Robinson (1960), which was a huge hit.

The Rank Organisation insisted Mills play the role of the priest in The Singer Not the Song (1961) opposite Dirk Bogarde.

Mills and Baker reteamed on an interracial drama, Flame in the Streets (1961), and an Italian-British war film, The Valiant (1962).

[citation needed] Mills began to move into character roles, supporting Hugh O'Brian in Africa Texas Style (1967) and Rod Taylor in Chuka (1967).

For his role as the village idiot in Ryan's Daughter (1970)—a complete departure from his usual style—Mills won a Best Supporting Actor Oscar.

On stage he did Veterans at the Royal Court, At the End of the Day (1973), The Good Companions (1974), Great Expectations (1975) and Separate Tables (1977).

Also on the small screen, in 1974 he starred as Captain Tommy "The Elephant" Devon in the six-part television drama series The Zoo Gang, about a group of former underground freedom fighters from the Second World War, alongside Brian Keith, Lilli Palmer and Barry Morse.

In the late 1970s Mills could still get lead roles in films, as shown by The "Human" Factor (1975), Trial by Combat (1976) and The Devil's Advocate (1977).

Mills's last cinema appearance was playing a tramp in Lights 2 (directed by Marcus Dillistone); the cinematographer was Jack Cardiff.

In the years leading up to John Mills's death, he appeared on television only on special occasions, his sight having failed almost completely by 1992.

In 1999, at 91 years of age, Mills became the oldest joining member of the entertainment charitable fraternity, the Grand Order of Water Rats.