Born in King's Cross, of a Devon family, he was a leading member of the London Devonian Association and claimed falsely to be born in Tavistock. He was educated at the University of London and won the Holts Scholarship in 1896 to study at Gray's Inn, where he was called to the bar in 1900. He married Ada Clark of Stoke Newington and the couple had a daughter. He also had a number of mistresses and fathered numerous illegitimate children. Coumbe served as Mayor of Stoke Newington for 1921-22. In March 1942 he suffered a serious injury in a fall, and he died six months later.