Born in Workington, O'Hagan started work at the age of fourteen for the United Steel Companies,[1] and immediately joined the National Federation of Blastfurnacemen, Ore Miners and Kindred Trades (NUB).
[1][2] He was successful, becoming a blastfurnace keeper before he took up full-time union work in 1939.
[1] In 1958, he was made an officer of the Order of the British Empire.
[2] O'Hagan served on the Iron and Steel Industrial Training Board and the National Safety Committee, and was a delegate to the International Labour Conference.
[4] After leaving his union duties, O'Hagan served as a director of British Steel Corporation's General Steels section until his final retirement in 1971.