Denis Payne was a senior MI5 officer who served in Northern Ireland in the 1970s. Payne relieved the MI6 officer based at Stormont Castle at some point in late 1973/early 1974. According to Paul Foot, Payne's appointment, with the new title of 'Chief of Intelligence' marked the point at which Northern Ireland became an MI5 preserve at MI6's expense.
Denis Payne - the man behind Operation Clockwork Orange
Powerbase page on Denis Payne, MI5 director of intelligence in Northern Ireland, said to be responsible for the Clockwork Orange psychological Warfare programme.