Hannon's family had a tradition of horse training — his father Harry was also a trainer. In fact, Richard started out as his father's assistant and took over Harry's licence when he retired in 1970. His first winner was Ampney Prince at Newbury on 17 April 1970. At that time, there were only a dozen horses in the yard and in the intervening years Hannon's stable grew to 60 horses by 1977, eventually becoming the largest in Britain in terms of number of horses - 270 in 2012. By the time of his retirement he operated from two sites - Herridge and Everleigh.