FORMER IRA BOMBER RECALLS PLOT TO KILL PRINCE CHARLES.

Byline: Warren Hoge The New York Times

It was to be the most audacious operation in the history of the Irish Republican Army - the killing of Prince Charles and his wife, the princess of Wales - and the organization needed someone it trusted.

It turned to Sean O'Callaghan, a member of the group since his teens who had proved his loyalty by building bombs, attacking police precinct houses with mortars, conducting robberies and killing two members of the security forces.

He was sent to London and provided with delayed timing detonators and 25 pounds of a powerful mining explosive called Frangex gelignite. The hit was scheduled for a night when the newly married prince and princess were to attend a charity benefit at a West End theater by the rock group Duran Duran.

O'Callaghan cased the theater, found the spot in the wall of a bathroom stall near the royal box where the bomb would fit and learned the time when cleaning women opened the restroom, giving him the two hours he would need to plant the device. ``It would have worked; it had a high chance of success,'' O'Callaghan said in a recent interview.

The 1983 plot failed, however, and one reason was that O'Callaghan was an informer for the Irish police special branch and British intelligence, the highest ranking IRA man, it later developed, ever to betray the clandestine organization from within.

Despite his cooperation with the authorities, O'Callaghan was sentenced to multiple life sentences for two homicides and 40 other admitted acts of terrorism. Now, after serving just eight years, he has been freed, just in time to enter the debate over Northern Ireland as an implacable and vitriolic foe of the IRA.

In particular, he has attacked the effort by Gerry Adams to gain respectability and a role in the peace process for Sinn Fein, the IRA's political wing, which Adams leads.

``I wish I could be confident about the prospects for peace, but I have sat behind too many closed doors with too many of the present leadership to be conned by the smooth presentations,'' said the 42-year-old O'Callaghan, a former member of the Sinn Fein executive council.

O'Callaghan was released from prison Dec. 6 under a rarely used procedure requiring approval of the queen. The timing was critical for the British government, for it introduced into the debate an insider who is forcefully making the same argument put forward by John Major, the British prime minister.

Although he helped jail some 50 IRA operatives and confiscate millions of dollars worth of arms, O'Callaghan said he wasn't overly concerned about his personal safety ``in the short term.''

O'Callaghan may be banking on the notion that maintaining a high profile is his best protection, that killing a public figure would not be in the best interests of a group seeking admission to peace talks.

Major believes the 18-month IRA cease-fire that ended with the bombing of a London office building in February was a ruse through which the organization gained political standing while it retooled its terrorist apparatus. He has rejected conditions set by Adams and John Hume, the mainstream Roman Catholic leader in Northern Ireland, for Sinn Fein's participation in peace talks, demanding that the IRA provide evidence of a ``lasting cease-fire.'' Adams and Hume argue that Major is sabotaging their effort to rebuild the peace process and that a ``precious moment'' is passing.

Enter O'Callaghan, who over the past two weeks has voiced shame at what he did for the IRA and urged Britons not to believe the pacific claims of Sinn Fein. He has testified before the Commons, given radio interviews and written articles for The Sunday Times, the newspaper that first made his double life public in 1992.