The parents of Mr O'Neill, who was born and lived in London, flew from their home in the Irish Republic yesterday to identify their son's body. Their other son, Shane, 23, is understood to be among the five men arrested during the early morning raids on Monday.
All of the suspects were still being questioned yesterday at Paddington Green police station. Armed officers carried out raids at four addresses and recovered a vast amount of home-made explosives, two lorries, car booby traps, and guns at a north London warehouse.
Eoghan and Teresa O'Neill, who are retired, yesterday travelled to London from their home in Kilbrittain, 30 miles from Cork. Their son was shot at a guesthouse in Hammersmith, west London and later died in hospital. Shane was also arrested at the address.
Dermot O'Neill was born and lived in London and, like his brother Shane, went to London Oratory School in south-west London. John McIntosh, the headmaster of the school, whose pupils include Tony Blair's son, Euan, said both were "well-behaved and pleasant".
There are reports that Dermot O'Neill was sentenced to 12 months in a young offenders' centre after being convicted of fraud and deception charges in 1988. The offences were linked to the Shepherds Bush branch of the Bank of Ireland involving a sum of pounds 75,000, a part of which was reportedly channelled to the IRA.
Alan Finn, 36, who lives opposite the brothers in Averil Street, said he saw Shane being arrested. He said: "He and his brother were very neighbourly. They didn't come across as being Irish because they both talked with Cockney accents."
Mr O'Neill's parents moved to Ireland from London two years ago when they retired. Mr O'Neill originates from Co Cork and his wife from Dublin. They also have two daugthers.
Dermot O'Neill was in Cork for his father's birthday a couple of weeks ago, according to local residents. Publican Charlie Madden said: "I'm shocked. This was a lovely lad who came home to see his father a couple of times a year." He added that the family never spoke about, nor got involved in, politics.
The Irish Republican Socialist Party, regarded as the political wing of the INLA, claimed yesterday that O'Neill had been unarmed when shot, and called on the media to investigate his death.
The other four men being questioned are known as Brian McHugh, James Murphy, Patrick Kelly and Michael Phillips, a 21-year-old, newly qualified engineer working at Gatwick airport.
Anti-terrorist officers continued to carry out a detailed search of the three raided properties in London and another property in Crawley, Sussex.
Early yesterday, the Irish police also carried out a series of raids on homes close to the southern side of the border in Co Monaghan and also in Co Longford. The moves were linked to the London operation but no one was arrested.
The explosives find in London has plunged the Northern Ireland peace process deeper into crisis. The clear indication that the IRA was intent on fresh bombings has hardened Unionist determination that the issue of decommissioning terrorist weapons must be dealt with at the top of the multi-party talks agenda - which has still not been agreed following weeks of wrangling by participants.Reuse content