Memorial service for top Garda IRA agent Sean O'Callaghan

Author Ruth Dudley Edwards was speaking ahead of the service at St Martin-in-the-Fields, Trafalgar Square, next Wednesday.

Mr O’Callaghan was understood to have been the Garda’s top agent inside the IRA, later going on to write a best-selling book detailing his experiences, The Informer.

He died aged 63 in August in Jamaica and his ashes were later scattered in his native Co Kerry.

“He might have found it very funny, but it never crossed our minds,” Ms Dudley Edwards said of the date of the service also being the first anniversary of the death of Sinn Fein’s Martin McGuinness, a former IRA leader.

In August Lord Trimble told the News Letter that Mr McGuinness phoned Sean during a tense time of Sinn Fein-UUP peace negotiations to ask if Trimble was “serious about working this agreement”. Sean had answered “yes”.

Speakers at the service will include Sean’s friends the one-time Cabinet minister Marquess of Salisbury and best-selling author Douglas Murray. Readers will include Lords Bew and Trimble and Professor Liam Kennedy from Tipperary.

Sean’s brother will read from his favourite poet, Patrick Kavanagh, and his son will read his poem about being an informer.

Among the charities for which there will be a collection are the benevolent funds of the RUC – he murdered DI Peter Flanagan – and the UDR – he was part of the unit that murdered Pte Eva Martin.

“Sean was haunted all his life by his terrible crimes, but unlike most terrorists, he faced what he had done with fierce honesty and exceptional moral courage,” Ms Dudley Edwards added.

Everyone who liked him is welcome to attend, she said, and is asked to make a reservation via [email protected].