1983 press report
O'Callaghan was named in the British media in connection with the IRA bombing campaign in England in 1983:
- Scotland Yard said it also wanted to trace one of Downey's IRA associates who recently arrived in Britain and might be armed. He was identified as Sean O'Callaghan, 30, a native of Tralee, County Kerry in the Irish Republic.
- A spokesman refused to give any other details about the men or how they were identified.
O'Callaghan has claimed that he was in England scouting for a bomb attempt aimed at Prince Charles and Princess Diana at the Dominion Theatre on Tottenham Court Road, and that the press coverage was arranged with his Garda handler to abort the operation. Downey's name was introduced to deflect some attention from him.
- But if O'Callaghan had infiltrated the England Department and if he had been sent to England on active service in 1983, why did he arrange for his cover to be blown after just ten days, making it impossible for him ever to be used in that way again? If O'Callaghan's version is to be believed, British and Irish Intelligence gave up the chance of an agent in the IRA's England Department and returned him to a relatively minor position in Kerry. It just doesn't make sense.
- Recent admissions by an IRA assassin turned informer that he led authorities to intercept a massive Boston-based IRA gunrunning operation in 1984 involving the Gloucester trawler Valhalla indicate that for years, the wrong man may have been suspected as the leak, Irish law enforcement sources say.
- O'Callaghan says that when the Valhalla sailed, he had cooperated only with Irish authorities. It was only later that his Irish handlers turned him over to their British counterparts. "The Brits wouldn't have killed anyone to protect me," he says. "I wasn't working for them."
- Irish police sources corroborate O'Callaghan's account, saying he did not begin working as an informant for MI5, the British intelligence service, until 1986.
- Besides, says O'Callaghan, even if British agents had killed McIntyre, the IRA would have eventually figured out through its own intelligence network that neither the IRA nor McIntyre's American associates were involved in his abduction.
- Sinn Fein member John Corcoran, 45, was killed in County Cork in March 1985. He had been tortured before being shot in the head.
- Months earlier, in one of the most significant successes ever achieved against the IRA, British and Irish security forces had seized the trawler Marita Anne as she headed for Kerry with a cargo of weapons. According to senior republican sources, the IRA held a 'court martial' before sentencing Corcoran to death as a long-term police informer.
- Among those involved was Sean O'Callaghan, unmasked last week as an MI5 agent. He had been passing information about IRA operations for years.
- A republican source in Kerry said yesterday that it now appeared that Corcoran was just set up to cover O'Callaghan's activities.
O'Callaghan gave himself up to police in Kent in November 1988.
- Sean O'Callaghan, aged 34, a former Sinn Fein councillor from Tralee, Co Kerry, walked into Tunbridge Wells police station and was transferred to Castlereagh Prison in Northern Ireland.
- The RUC is questioning him in connection with offences in Ulster. Mr O'Callaghan, who left Tralee in November 1985, had telephoned an Irish newspaper to say he was taking the action in the hope of dispelling rumours in his home town that he had become a police informer.
When he was named by Scotland Yard Mr O'Callaghan denied being in Britain during the election. He had lived in Britain for a few years but left in 1978.
O'Callaghan was tried at Belfast Crown Court in April 1990.
- O'Callaghan, who represented himself in court today, pleaded guilty to the charges, which also included conspiracy to murder, causing explosions, possessing explosives and firearms and IRA membership. He admitted the murder of UDR member Mrs Eva Martin, who was killed during a rocket attack at Clogher UDR base in May 1974, and the murder of RUC inspector Peter Flanagan, shot dead in a public house in Omagh in August of the same year. In a statement from the dock O'Callaghan, originally from Marian Park, Tralee, County Kerry, said his reasons for admitting his activities did not concern the court, but he was not and would never make any apologies for his activities. "I spent most of my life involved in the republican movement in what I believed was a valid and just struggle. "I would have thought myself cowardly and remiss if I did not set out to end British rule and unify my country" he told Mr Justice McCollum. The judge said he wished to study the voluminous and detailed papers in the case before passing sentence.
O'Callaghan was given two life prison terms and concurrent sentences totalling 539 years after admitting 42 crimes. The judge made no recommendation as to how long he should serve as his crimes were committed 15 years previously.
- A SENIOR IRA prisoner, jailed two years ago, has claimed that he was working for MI5 when he was sent on bombing missions to Britain. One of his alleged targets was the Prince and Princess of Wales.
- In interviews at Maghaberry prison, near Belfast, Sean O'Callaghan, aged 38, from Co Kerry, has promised to reveal more details about IRA operations over the last 15 years.
- It is believed that he is planning to write a book on his time in the organisation. Security sources yesterday declined to comment on whether Mr O'Callaghan had ever worked for them.
- O'Callaghan, 38, is on an IRA death list after it was revealed that he became a double agent for MI5 and the security services in his later years with the terrorist organisation.
- The Sunday Times, which revealed the alleged royal bomb plot yesterday, denied paying O'Callaghan for his story and said he was making the disclosures because he accepts that his informer days are over and wants public recognition.
- But one security source said: 'It is fair to say that he is a cunning, charismatic and manipulative person.
- 'I would suspect that his motive is more in the hope of making money than any sense of public duty and recognition.
- 'It could be that he also has some misguided hope that by making the claims about his life as a secret informer, he may win public support for an early release from his sentence'.
O'Callaghan went on Hunger strike in December 1992, "because, he says, his plans to write and publish details of his activities have been censored by the prison authorities." He reportedly ended his hunger strike after ten days.
- O'Callaghan explained his decision to end the strike in a statement from Musgrave Park Hospital, Belfast. "I decided I wanted to continue living in order to do as much as possible to harm the IRA," he said. "I will continue to campaign against paramilitary terrorism. I have no axe to grind against the RUC." 
In August 1994, O'Callaghan claimed that the IRA met an Iranian official in Galway in 1984.
In a 1996 Spectator article, O'Callaghan claimed that the Irish Catholic Church is "a rather unique form of criminality" which "consistently conspired with the worst elements of extreme nationalism to produce a dogma based on the racial purity of a mythological 'Irish race"'.
In 2000, O'Callaghan attended a United Nations Convention against Transnational Organised Crime where Professor Roy Godson was among the speakers:
Following the publication of the Stevens report into collusion in 2003, O'Callaghan claimed that the murderered solicitor Pat Finucane was an IRA member.
- I knew Pat Finucane reasonably well. I first met him in 1980 at a high-level IRA finance meeting in Letterkenny, Co Donegal. The meeting took place in a private room above a public house. Also present were Gerry Adams, the now-dead Tom Cahill, Pat Doherty (now the MP for West Tyrone) and several others.
It is notable that O'Callaghan did not name anyone who could authenticate this account, except the two Sinn Féin MPs, whose views he could be expected to discount.
Omagh Civil Trial
In January 2009, O'Callaghan was due to testify against jailed dissident republican leader Michael McKevitt in a civil action over the Omagh bombing. His testimony was delayed when McKevitt's lawyers responded by requesting police notes from debriefings at Tunbridge Wells police station in England and then Gough Barracks, Armagh, in 1988 which O'Callaghan referred to in his autobiography, The Informer. McKevitt's barrister Michael O'Higgins SC, said he wanted to raise the Sean Corcoran case. The PSNI was initially unable to locate any documents.
Two weeks later, lawyers for the PSNI told the court that they had found 57 sets of interview notes, most of which focussed on O'Callaghan's role in the murders of special branch detective Peter Flanagan and soldier Eva Martin during the 1970s. Judge Mr Justice Morgan said the files “would appear to exclude quite a bundle of material which Mr O’Callaghan, it is said, refers to in his book, which might well be material relevant to whether his evidence is undermined”, presumably a reference to the Corcoran case.
Life sentence reports disclosed to the McKevitt team included a letter from a deputy chief constable detailing information O'Callaghan had supplied over the years. According to barrister Kieran Vaughan, this stated: “His bizarre behaviour whilst in prison precluded the Crown from placing reliance on O’Callaghan as a witness.”
- Scotland Yard Warns of IRA Attack, Orders Guards for Candidates, Associated Press, 26 May 1983.
- The Informer, by Sean O'Callaghan, Corgi, 1999, p209.
- [O'Callaghan - the truth O'Callaghan - The Truth], by Brian Campbell, An Poblacht, 27 February 1997.
- Valhalla case now a little murkier; Quincy man seen as fall guy in leak, by Kevin Cullen, Boston Globe, 24 December 1992.
- IRA man tells a tale of betrayal, by Kevin Cullen, Boston Globe, 29 January 1995.
- MI5 'arranged murder';UNDERCOVER AND ON THE STREET . . . THE BATTLE AGAINST THE IRA, Mail on Sunday, 6 December 1992.
- The Informer by Sean O'Callaghan, Corgi Books, 1999, pp.312-317.
- RUC quiz man sought by Yard; Sean O'Callaghan, The Times, 2 December 1988.
- No place to hide with us, by Walter Ellis, The Times, 9 July 1991.
- 'I spared Diana and Charles'; SUSPICION AS AN IRA KILLER SEEKS 'PUBLIC RECOGNITION', by Peter Rose, Daily Mail 30 November 1992.
- IRA MAN ADMITS CATALOGUE OF MURDER AND TERROR, Associated Press, 27 April 1990.
- TWO LIFE SENTENCES FOR IRA KILLER 'THE JACKAL', Press Association, 2 May 1990.
- JAILED IRA MAN CLAIMS HE WENT ON MISSIONS AS AGENT OF MI5, by Owen Boycott, The Guardian, 30 November 1992.
- 'I spared Diana and Charles';SUSPICION AS AN IRA KILLER SEEKS 'PUBLIC RECOGNITION', by Peter Rose, Daily Mail 30 November 1992.
- Hunger strike inmates alleges plot, by Gerry Moriarty, Irish Times, 5 December 1992.
- IRA killer ends hunger strike, Press Association, 4 July 1993.
- TV NAMES IRA 'TERROR CHIEF'; SINN FEIN LEADER IS ACCUSED IN TV PROBE, by Robert Rodwell and Charles Reiss, Evening Standard 25 August 1993.
- Newspaper says Iran financed IRA, United Press International, 21 August 1994.
- EX-IRA KILLER SAYS PRIESTS 'TREATED US AS HEROES', by Roger Williams, Press Association, 18 April 1996.
- The Mafia Culture, by Chris McGimpsey, Belfast Telegraph, 15 December 2000.
- Sean O'Callaghan, Finucane should not have been killed - but he was in the IRA, Telegraph, 18 April 2003.
- Missing IRA files branded "totally unsatisfactory, Belfast Telegraph, 7 February 2009.
- Police find lost evidence for Omagh civil case, Belfast Telegraph, 21 February 2009.