John was born in Chelmsford in the summer of 1918 to Reginald Alfred Clark and his wife Jessie Allen. In 1911, his parents were living at 18 Burgoyne Road, South Norwood and his father was described as a tailor, dealer and an employer. He had been born in Bishops Stortford in 1884. Jessie came from Brigg, Lincolnshire where her father was a confectioner. John had an older sister.

John was a chorister at Christ Church.

He was gazetted as a Pilot Officer on probation on 6 November 1939.

He joined 206 Squadron and was killed on 22 May 1940.

He is commemorated on the Runnymede Memorial, Panel 7.

His parents lived in Little Baddow, Essex.