The son of Irish-born John Lionel Darby, the former Dean of Chester, Arthur Darby was educated at Cheltenham College before going to Clare College, Cambridge where he graduated with a BA and was a three times rugby Blue in 1896, 1897 and 1898. He obtained his MA in 1910. Darby was selected for the Barbarians in 1897 and two years later played his one and only international match for England, in the defeat by Ireland at Lansdowne Road, Dublin. A forward, he played for the Moseley Wanderers XV at the 1900 Paris Olympics and other representative honours included playing for the South in the annual contest against the North, and also gaining selection for the combined Oxford and Cambridge University team on several occasions. Darby was a schoolteacher in Guernsey from 1902-04 and then worked as an interpreter and instructor to the Atlantic Fleet in 1905 before taking a post as an assistant master at the Royal Naval College, Dartmouth. He spent 29 years teaching at the College and from 1932 until his retirement he was their Head of Languages. He served in World War I as a lieutenant with the Royal Navy Volunteer Reserve