More than a decade ago, Roddy Doyle began to write a trilogy of novels that would re-examine the history of Ireland in the 20th century through the experiences of its central character. In A Star Called Henry, Henry Smart emerged from the Dublin slums to become the youngest participant in the Easter Rising and a famous hard man in the years of violence that followed. Oh, Play That Thing showed him in enforced exile in America and traced his adventures amid the speakeasies and jazz clubs of the Prohibition era. In this final volume of the trilogy, Smart has become a man wrestling for possession of his own life history.

As The Dead Republic opens, the year is 1951 and Henry has returned to Ireland in the entourage of the film director John Ford. Some time earlier, despairing and disillusioned, he had wandered into the Utah desert to die, only to be discovered when Henry Fonda stepped off the set of a western to empty his bladder and pissed all over him. Now he has become a kind of mascot for the mythmaking Ford, a man eager to bring to the cinema his fantasies about the world of his Irish forebears. The director employs Smart to transform his Irish rebel life into a screenplay. As Ford continues to make westerns to pay the bills, he dreams of the day when the tales he hears from Henry can be retold. “He knew what I was doing,” Henry says. “I was reclaiming my life. And I knew what he was doing. He was making me up.” In the end, the make-believe world wins out over remembrance of reality. The film Ford is making becomes The Quiet Man and, as anyone who has seen that exercise in rose-tinted nostalgia knows, the Ireland it depicts is a long way from any country that Henry Smart might recognise. “I’d tried to tell the truth,” Henry says of his contributions to Ford’s work, “but I’d ended up inventing Ireland.”

In the second half of The Dead Republic, the narrative fast-forwards to the years of the Troubles. The battle with Ford for possession of his own past is long over. Henry has settled near Dublin and is working as caretaker at a local school when he is caught up in a bomb blast. His identity as Republican hero revealed by the media, he is taken up by more people who, like Ford, want to reshape his story for their own purposes. New generations of Republicans rush to claim him as a precursor. “I was Celtic mythology walking towards them,” Henry wryly remarks. As the 1980s open and the hunger strikers in Long Kesh prison begin to die, the ancient activist becomes a valuable propaganda tool for the Provisional IRA. “They were going to show me off ... I’d make sense of the young men starving themselves, racing to become as old and as noble as me. I’d be their living saint.” Henry has more personal concerns - the demands of his ageing body, an improbable reunion with the woman who was his wife decades earlier - but the mythology of the Republican movement and the politics of violence engulf him once more.

Like its predecessors, The Dead Republic skilfully weaves together its facts and its fiction. Henry’s narrative voice retains the vigour, the energy and the directness it possessed from the beginning of his story. Yet the final part of the trilogy suffers from Doyle’s determination to cram so much significance into the trajectory of his antihero’s life. No character other than Smart and Ford carries much conviction. Plausibility in the development of the plot is sacrificed to the requirement that Henry’s experiences must be a mirror in which Irish history is reflected and refracted. The two halves of the novel, divided by 20 years, seem almost to belong in different books and perfunctory attempts to yoke them together towards the end fail to persuade.

Over the course of three books, Henry Smart has proved to be Doyle’s most memorable fictional creation but his struggle to escape the confines of a portrait of him others are committed to painting does not turn out to be his finest.