William Ernest George Johnston was the son of Sir James Johnston (a previous Lord Mayor of Belfast in 1918).

William Johnston was educated at Campbell College and Queen’s University. He worked in his father’s flax business and went on to become a director, and subsequently chairman, of the company.

Johnston entered the Belfast Corporation in 1941, representing St Anne’s ward. He was appointed as High Sheriff of Belfast in 1947. As Lord Mayor he was an ex officio member of the Senate of Northern Ireland. He was made a Deputy Lieutenant of Belfast in 1950 and knighted in June 1951.

During the Second World War Sir William and his wife established and managed a canteen for troops at the Girl Guide Headquarters on Malone Road. He also volunteered as Chief Air Raid Warden of South Belfast District.

Johnston acted as chairman of the Committee of Management of the Belfast Savings Bank. He was a member of the Ulster Unionist Council and was a member and president of the Ulster Reform Club.