Mastel was educated at Tottenham Grammar School and joined the Metropolitan Police as a Constable in 1937.
He served as a pilot in the Royal Air Force Volunteer Reserve from 1941 to 1945, being commissioned from the rank of Flight Sergeant in May 1944[1] and promoted Flying Officer in November 1944.
[2] Rejoining the police, he was promoted Sergeant in 1946, Inspector in 1951, and Superintendent in 1955.
He was appointed Commander of the Order of the British Empire (CBE) in the 1969 Birthday Honours, having been promoted Deputy Assistant Commissioner (Personnel).
[6] He retired on 31 December 1976[7] and was appointed Commander of the Royal Victorian Order (CVO) in the 1977 Birthday Honours.