Profile: Freddie Scappaticci - From lowly footsoldier to a man feared by hardened gunmen
He was small in stature but with a huge reputation.
Freddie Scappaticci, who has always denied being the agent code-named 'Stakeknife', fled Northern Ireland in 2003 following media revelations.
He was alleged to be the highest-ranking British agent in the Provisional IRA and was feared by even the most-hardened IRA gunmen and bombers.
As a member of the so-called 'Nutting Squad', he was charged with rooting out, interrogating and dealing with suspected informers.
He also vetted IRA recruits.
'Scap' was the grandson of an Italian immigrant who moved to Northern Ireland in search of employment.
He lived and worked as a builder in west Belfast and was interned in the early 1970s alongside Sinn Féin leader Gerry Adams and a number of other high-profile republicans.
Having joined the IRA as a low-level footsoldier, he quickly rose through the ranks, becoming deputy head of the movement's notorious internal security unit.
It is alleged a brutal punishment beating persuaded Scappaticci to become a double agent known as Stakeknife, first with the Royal Ulster Constabulary Special Branch and then with the British army's Force Research Unit - a shadowy undercover outfit linked to the murder of Catholic civilians.
As a prized asset, Stakeknife reportedly received payments of up to £80,000 a year for information about kidnappings, bombings and shootings.
He was named publicly for the first time in 2003 by disaffected army agent Kevin Fulton, a South Armagh soldier who had infiltrated the IRA for the intelligence services.
Fulton, who had fallen on hard times, threatened to unmask Stakeknife in a row over money.
Scappaticci denied the claims, describing them as "reckless and extremely damaging".