Like five of his brothers, Geoffrey Coles was educated at Winchester College and studied practical engineering after leaving school, subsequently working for the Great Western Railway Works at Swindon, before moving to Cornwall and living off private means.

Geoffrey was part of the Great Britain shooting team at the 1908 Summer Olympics in London. He won a bronze medal in team pistol shooting and placed 11th voerall in the individual pistol event.

During the First World War, Geoffrey enlisted as a private with the 24th battalion of the Royal Fusiliers, known as the Sportsmen’s Battalion, formed of leading sportsman of the day, including footballers, cricketers, and other athletic and sporting personnel.

In November 1915, his battalion went to France, and two months later Geoffrey was killed by an exploding rifle grenade whilst on outpost duty at Festubert. Geoffrey is buried at Brown's Road Military Cemetery.