SirJohn Stalker. PHOTOGRAPH: ITV/REX FEATURES

HIS BOOK WAS a gripping, bestselling thriller, but The Stalker Affair was no work of fiction. John Stalker's account of his failed investigation into an alleged 'shoot-to-kill' policy by the RUC was a publishing sensation in 1988, blowing the lid on the activities of Northern Ireland's security forces, and detailing a dirty tricks campaign to discredit him at home.

It all began in 1984 when Stalker, then deputy chief constable of the Greater Manchester police force, was sent to Northern Ireland to investigate allegations that RUC officers were carrying out assassinations, after six suspected IRA members were shot dead in suspicious circumstances. Stalker was well qualified to head the investigation. An expert in world terrorism, he had risen through the ranks via the Serious Crime Squad, the Drugs Squad and the Bomb Squad, and in 1978 had become the UK's youngest detective chief superintendent.

He immediately locked horns with then chief constable of the RUC, Sir John Hermon, whom he found to be uncooperative. But Stalker never got to finish the investigation, because he was suddenly suspended from the force following allegations that he had been socialising with Manchester's so-called 'Quality Street Gang'. The allegations were disproved, and Stalker was cleared of misconduct and reinstated in his job, but he remained convinced he had been fitted up.

'I believe, as do many members of the public, that I was hurriedly removed because I was on the threshold of causing a major police scandal and political row that would have resulted in several resignations and general mayhem,' he wrote in his autobiography. He could no longer work with colleagues who had accused him of misconduct, so he quit the police force.

His expertise in the fields of policing and security didn't go to waste, however; he set up his own security consultancy, and wrote articles on crime and security for several UK national newspapers. He became an in-demand after-dinner speaker, and the go-to guy for media quotes on such high-profile news stories as the death of Moors murderer Myra Hindley, the killing of Jean Charles de Menezes by the London Metropolitan Police, and the disappearance of Madeleine McCann.

In 2004, he led a consortium that included Sun editor Kelvin McKenzie in bidding for a commercial radio station in Manchester. He dabbled in theatre, starring as the Narrator in a touring production of the Rocky Horror Show , though he declined to don the stockings and suspenders usually worn by the character. He also became a well-known television personality, presenting the Crime Stalker show on regional TV for six years, and starring in ads for double-glazing, garage doors and awnings, along with his dog Drummer. In 2006, his wife Stella was badly mauled by two rottweilers, prompting Stalker to call for reforms in the laws governing dangerous dogs