John Sydney Gatehouse was baptised in Hackney in London. His father was Arthur Gatehouse and mother Mary Catherine Bromley Gatehouse. Arthur was a coachman. By 1901, Arthur was a widower with three children at home, the youngest of whom was John aged 9. Eleven years later, aged about 20, John was appointed junior mechanic in the Postal Service Stores Department in 1912.

He left the Postal Service to serve with the Post Office Rifles in the First World War. John Gatehouse and Arthur Dudley (who is buried very close by in Row C, Grave 6) were the first two members of the Post Office Rifles to be laid to rest in Post Office Rifles Cemetery, having died on the same day. This was the day after the unit entered the front-line trenches near Givenchy in May 1915.

His next-of-kin was not in contact with the Army or the War Graves Commission, so his headstone does not have his forenames or his age at death or a personal inscription provided by his family. John is remembered with pride by the Post Office Remembrance Fellowship.