Educated at a leading London Catholic school from where he went into a banking job with prospects, this was a man you might have expected to be cheering Tim Henman at Wimbledon and Atherton at Lord's. Surely an Englishman through and through. How could he even call himself Irish, let alone sympathise with the IRA?
But I am not surprised by Mr O'Neill's behaviour. Like him, I was born in England of Irish parents, and I find his outlook all too easy to understand - given the dangerous romanticism attached to Irishness and the difficulty one has in reconciling that with Britishness.
And I suspect that among the eight million people of Irish descent living in Britain (a million of them Irish-born) few will lack at least some insight into Diarmuid O'Neill's thinking. He is typical of so many second generation emigrants who struggle to define themselves, to draw together two notions of themselves - as British and Irish - that for so much of history have seemed contradictory.
This is a problem that has become acute for children growing up in Britain during the past two decades, watching the violence of Northern Ireland. The strain on O'Neill to sort out this dilemma must have been immense as he grew up.
His parents Eoghan and Theresa had emigrated from Ireland, but had dreamed of a return. Such dreams can be destabilising for a child, making it more difficult to feel a sense of belonging to Britain. In Mr O'Neill's case, Ireland could have begun to be seen as a place harbouring the good things in life - holidays, friendliness, pleasure - and Britain more of a prison sentence, a place for work and social alienation. As in so many emigrant families, O'Neill may have been raised amid the old tales of rebellion. Like him, I had grandparents who lived through the Easter Rising - a grandmother who was 18 in 1916, who lived in the barracks town of Tipperary and was a staunch republican.
Doubtless, O'Neill will have been steeped in the history of atrocities committed by the British "Black and Tans". He would have heard the Dubliners singing songs such as "Kevin Barry", the tale of a young rebel being executed. He may have known that the socialist leader James Connolly had to be tied to a chair when he was executed because he had been so badly wounded.
His family would have remembered Donal O Buachala who won a seat for Sinn Fein in the party's 1918 general election landslide victory, as British rule collapsed. Was Diarmuid, I wonder, told that Eoghan Roe O'Neill, his father's namesake, was one of the Irish military leaders of the 17th century, securing a famous victory at Benburb in 1646?
These are the seeds that can plant in a child an unrelenting belief that his soul is Irish, whatever may have been going on in England. But O'Neill would have faced other influences, too.
Catholic schools studiously avoid all mention of Ireland or Irish history. His school in Fulham, the London Oratory, a famous bastion of English Catholicism, would not have encouraged Irishness. And perhaps trips to Ireland produced fresh confusion. As a child, on frequent summer holidays "home" to Ireland, Diarmuid would have been taunted by relatives for his English accent. Did they call him "the sassenach" - a pejorative word for English?
He used to go on holiday in west Cork, a strongly republican area, scene of some of the most vicious killings, by all sides, in the civil war of the 1920s. Did O'Neill find that even his red hair and his Gaelic name were not enough to establish his credentials. Did he feel he had to make some other more dramatic gesture to prove who he really was?
Most people like O'Neill live with their duality, their confusion, defining themselves as a complex of Irishness and Englishness. It can be a creative process. Mary Hickman, of the University of North London's Irish Studies Centre, has surveyed school children born of Irish parents. "In every study you find that no more than 20 per cent ever call themselves simply English. They describe themselves as mixtures."
And the Irish in Britain don't generally get involved in politics - they like to keep a low profile for fear of being considered a threat. Irishness for them is a family, domestic affair to be celebrated, perhaps, in the pub.
But something made Diarmuid O'Neill decide to be radical. He chose to negate his English upbringing completely and describe himself as totally Irish. Perhaps the crucial factor was his parents' decision to buy a place in Ireland, to which they eventually moved two years ago when they retired. Or maybe he wanted to emulate some of those historical, heroic figures with whom he grew up.
Or perhaps the key influences were political events in his upbringing. Born in 1969, his first television memories would have been of Belfast in the Seventies, echoing the stories told of the Twenties. And then there was the decade in which O'Neill became a teenager. He has been pictured with an edition of An Phoblacht, the republican newspaper, which commemorates the death in 1981 of the IRA hunger striker, Bobby Sands.
The hunger strike politicised many second generation Irish people, who campaigned within the old GLC, the Labour party and London Labour councils for nationalist political objectives. In that picture, Diarmuid O'Neill looks confident and happy. The fantasist at last knew who he was.Reuse content