A member of the Ulster Defence Association (UDA) – the largest loyalist paramilitary organisation in Northern Ireland – he first held the rank of lieutenant colonel and later was made a brigadier.

According to journalists Henry McDonald and Brian Rowan, and the Pat Finucane Centre, he became a Royal Ulster Constabulary (RUC) Special Branch informer.

[n 1] According to his daughter, Linda, he joined the UDA after a Provisional Irish Republican Army (PIRA) bomb exploded at the Balmoral furniture showroom in the Shankill Road in December 1971, killing four people, including two babies.

[4] During the Ulster Workers' Council Strike of May 1974 Lyttle was, along with UDA leader Andy Tyrie and Ken Gibson of the Ulster Volunteer Force (UVF), one of three loyalist paramilitaries chosen to accompany the three leaders of the main unionist political parties, Harry West, Ian Paisley, and Ernest Baird, to a meeting with Stanley Orme, the deputy to the Secretary of State for Northern Ireland Merlyn Rees, in which the government representative attempted unsuccessfully to have the strike terminated early.

[10] Together with Tyrie, Vanguard Assemblyman Glenn Barr, his ally Andy Robinson and Newtownabbey-based Harry Chicken, Lyttle travelled to Libya where he met Colonel Muammar Gaddafi about obtaining weapons and money for the loyalist cause.

[12] In 1977 he helped form a think tank with UDA Commander Andy Tyrie and South Belfast brigadier John McMichael; this was called the New Ulster Political Research Group.

[13] In January 1990, Lyttle, along with his son, "Tosh", was arrested by the John Stevens Enquiry team after his fingerprints were found on a stolen classified document which was a security forces list of suspected republicans, likely to be used by loyalist paramilitaries for targeting people to be assassinated by hit squads.

He was brought before Belfast's Crumlin Road Court where he was convicted of receiving and passing on classified security force intelligence files and intimidating potential witnesses.

[5] Journalists Henry McDonald and Brian Rowan, in company with the Pat Finucane Centre, later revealed that Lyttle was an informer working for the RUC's Special Branch with the codename "Rodney Stewart".

According to Andy Tyrie, Lyttle was reluctant to become personally involved in the Finucane killing, as he feared that his rank of brigadier would make him a likely target for the inevitable IRA retaliation.

When the name Frederick Scappaticci came up, Nelson's FRU handlers became alarmed as Scappaticci—allegedly known as "Stakeknife"—was one of their most important agents, having infiltrated the Provisional IRA's Internal Security Unit or "Nutting Squad" as it was commonly referred to.

On 9 October 1987, Lyttle sent out a UDA hit squad, headed by Sam McCrory using the cover name "Ulster Freedom Fighters"[n 2] to Notarantonio's home where they shot him to death in his bedroom.

[17] With McMichael dead, Tyrie having resigned in March 1988 (following an attempt on his life) and Craig being assassinated by UFF gunmen in October 1988, Lyttle was one of the few veterans to remain in power and his incarceration during the Stevens Enquiry was to prove the catalyst for his removal from command, with Tommy Irvine succeeding him as West Belfast brigadier.

[21] Held in Crumlin Road Gaol from July 1991, word was sent into the prison by a new group of "Young Turks"—emerging leaders from the Shankill—that Lyttle was to be ostracised by the other UDA inmates.

[5] His second son, John, a journalist who writes for The Independent, has described his father as a "hard man" who liked to read James Bond novels, and watch western and gangster films.