BRIGADIER Gordon Kerr is one of the most high-achieving soldiers in the British army - but he is also one of the most controversial men to have ever put on a military uniform. He is seen as the mastermind of the Dirty War in Northern Ireland - which saw multiple murders carried out by double agents who were working for British intelligence inside terrorists organisation.

The machinations of the Dirty War are the stuff of spy novels. In some cases, agents were allowed to carry out acts of terror, including murder, simply to keep their cover inside paramilitary groups. In other cases, officers who ran agents - known as handlers - passed intelligence to their informants which was then used to prepare assassinations. The Force Research Unit which Kerr headed was the key unit involved in running agents.

However, it’s a long way from Aberdeen where Kerr was born in 1948 to the back streets of Belfast or the bandit country of south Armagh. After graduating from a Scottish university in 1970, Kerr was commissioned in the Gordon Highlanders - and his talents quickly became obvious. His high level of education, which was relatively unusual for officers at the time, marked him out when he arrived at Glencorse, the training depot for the British army in Scotland, in 1971.

Second Lieutenant Kerr - army number 489090 and nicknamed Craigie by his friends - was posted to Cyrpus, and then to Northern Ireland in 1972, at the time when the Troubles were at their most bloody.

He was appointed an Intelligence Officer and began his undercover work. Dressed in civvies, he grew long hair to fit in with the civilian population, and drove an undercover scout car which was permanently being resprayed. By the time he finished his first tour of duty, he’d helped arrested four leading Provos. In 1974, he was made a captain and posted to the British army’s Intelligence Training Centre in 1975.

He was briefly with the ‘Det’ - the SAS-trained 14th Intelligence Company, the forerunner of the FRU - before been sent to the army’s HQ in Ulster and transferring from the Gordon Highlanders to the Intelligence Corp.

He vanishes off the map for a while, but by the early 1980s he was a major and posted to Berlin at the height of the Cold War. His job was taking on the Soviet KGB and the East German Stasi. Colleagues from that period found him too maverick, though they still praised him as a brilliant spy. One described him as ‘the spook’s spook’.

In Berlin, he was commander of Three Intelligence and Security Company, known as Three I-Spy. Stasi files show that Kerr’s men carried out more ‘flag tours’ - secret intelligence missions - than the French and US military intelligence put together. One officer who served with Kerr said his tactics were ‘pointlessly aggressive’.

Men who served with Kerr at the time describe him as ‘drunk with power’ - a brilliant soldier who lived by his own rules and was prepared for the ends to justify the means as long as that was in Britain’s interests.

After Berlin, he was a senior instructor with the Special Intelligence Wing in Ashford, Kent. At Ashford, Kerr and his Northern Irish wife - a school teacher who we have chosen not to name - were later involved in resettling British army agents whose cover had been blown in Ulster.

In 1987, Kerr, now a colonel, became Officer Commanding the FRU. It was then that civilians started to die in Ireland at the hands of loyalist gunmen aided and abetted by the security forces. One FRU source said: ‘My unit was guilty of conspiring in the murder of civilians in Ulster on about 14 occasions. We were able to take out leading Provos with the help of the UDA. It was a great military coup.’

One of the FRU’s main agents was the loyalist Brian Nelson, a former Black Watch solider who became the UDA’s chief intelligence officer. Nelson was later convicted of 20 charges, including five of conspiracy to murder and sentenced to 10 years in prison, even though Kerr gave evidence for him in court using the cover name Colonel J. Pat Finucane, a prominent human rights lawyer who represented republicans, was killed in 1989 after alleged collusion between FRU officers and loyalist paramilitaries, including Nelson. Kerr was later promoted to Brigadier.

There have been accusations that if FRU handlers discovered one of their terrorist agents was being targeted by rival paramilitaries that they would redirect assassins to innocent civilians in order to protect their informers. There are also claims that the FRU callously allowed agents, who were deemed to have ‘passed their sell by date’, to be captured, tortured and killed rather than help extract them from Ulster. The IRA’s Internal Security Unit, which Stakeknife helped run, is known to have used grotesque acts of torture on those they suspected of being a ‘tout’ or informer. Such torture included sitting victims naked on top of electric cookers.

Kerr has what is termed ‘protezione’ - the Mafia word for protection. After his time in Ulster, he was made military attache to the British embassy in Beijing - making him the effective joint number two in Britain’s entire military intelligence operation. His promotion would have been approved by the then chief of the defence staff, General Sir Charles Guthrie, who was also Int Corp’s colonel-commandant.

After Beijing it is unclear what path Kerr’s career took, though there were rumours he was involved in British military intelligence in Iraq. However, the Herald on Sunday has learned that Kerr has now retired from the army - potentially making it easier for any detectives to question him about the activities of Stakeknife and the FRU.

The MoD said with respect to Kerr and Operation Kenova: ‘We are assisting police in their investigation. As the investigation is ongoing it would be inappropriate to comment further.’