At one time, the commissioners were either retired military officers or civil servants. Sir John Nott-Bower, who served as Commissioner from 1953 to 1958, was the first career police officer to hold the post, despite several previous Commissioners having served in senior administrative positions in colonial forces, and the Metropolitan Police itself. Nott-Bower's successor Sir Joseph Simpson was the first Commissioner to have started his career at the lowest rank of Constable. However, Sir Robert Mark, appointed in 1972, was the first to have risen through all the ranks from the lowest to the highest, as all his successors have done.