A timely reminder of the Irish Republic's brush with a kind of ethnic cleansing

Most of those who left were either frightened by IRA attacks or unwilling to live in a state with a dominant Catholic ethos

I doubt that I have read a book as moving in at least a decade. Now there's a claim. But, oh, does this novel deserve rapture. At the age of 74, William Trevor has produced a masterwork. The Story Of Lucy Gault was nominated this week for a Booker Prize, which I fervently hope he wins. Ladbrokes have him down at 2/1 favourite. Trevor has been nominated several times before, but has never won. This must be his year. Lucy Gault is transcendent literature, an elegy for a vanished world, but most triumphantly a homage to the gift of redemptive love.

I recommend it to all who are heart-sore and troubled, to every lost soul who has made a life-changing mistake, and to anybody who is interested in the history of modern Ireland. It is not that William Trevor has written a political book, but Lucy Gault has lessons for all who want to see an Ireland finally at ease with itself and its different traditions.

Trevor's story begins during the Anglo-Irish War of 1920-22 and ends in the age of the internet. He writes of the dwindling community of southern Irish protestants with melancholy but never sentimentality. Trevor has created a story that has universal resonance, but its characters are intimately connected to a particular landscape. This is not simply a question of geography, but of language and history. Too often, in Ireland, our struggle to come to terms with the past has seemed like a series of fractured conversations, shouted through the noise of a storm.

Thankfully we had writers like James Joyce, Sean O'Faolain, and Frank O'Connor, who sought to translate our history in terms not circumscribed by tribal loyalty. The Story of Lucy Gault belongs in that most honoured tradition of Irish writing: the voice of the instinctual outsider who understands his country far better than any of its public patriots, an outsider who understands because he loves. At the heart of the novel is a child's act of defiance, which sets in train a series of tragic events. By the end the child has become a woman and, in the case of this reader at least, one feels the most extraordinary mixture of celebration and loss.

I must declare a particular interest. The countryside which William Trevor describes is the home place of my mother's people. It is also where I have spent every summer of my life since infancy. He has changed some places names, but I think I recognise the location of the big house at the heart of the novel. Perhaps it is a wishful assumption on my part, but I suspect that the place the writer calls Laherdane is near Ardmore on the East Cork/West Waterford border, near the beach at Ballyquin, where William Trevor himself spent time as a child.

I broke my ankle near that beach in my early teens. I was escaping in the dark because I thought I was being chased by a father who did not want me courting his daughter. He wasn't chasing me and his only comment many years later was to say: "God but you've got very big since I saw you last."

That was the longest time ago. Now I walk the beach with my wife and child. There is a big house situated back from the beach, occupied now by a local auctioneer, which I fancy is the model for the home of the fictional Captain Everart Gault, his wife Heloise and daughter Lucy. The town of Enniseala in the book is probably Youghal at the mouth of the River Blackwater with its "squat lighthouse" and beach upon which the timbers of ancient coastal defences have survived the battering of endless winter storms. I might, of course, be wrong. The towns, villages and beaches described by William Trevor may be a composite of places he has known, though I do remember him mentioning Ballyquin once in a short story.

I should reveal a second interest. Although baptised a Roman Catholic, I grew up with close connections to the Protestant community in Cork. My parents always strove to live outside the narrow Catholic/nationalist consensus that had enveloped the country of their own childhood. They were both Catholics and both proud of their Irishness. But they knew both were very different; true Irishness was not dependent on being Catholic.

My mother spent more than three decades of her life teaching in a Protestant school; many of her closest friends come from among that small community. The girls at the school discos she ran had names like Penny and Sophie and not Siobhan or Eileen; they went to Sunday service and not mass. In the hallway of the school was a great brass plaque inscribed with the names of the boys of Cork Grammar School who had fallen in the Great War. (Thousands of Irish Catholics fell in that war, too, but our government was disinclined to honour them).

By the time I was a teenager, the Protestants of the republic were no longer regarded, by most of us anyway, as part of some strange aristocracy. Except among the wilder elements of republicanism there was little attempt to visit the sins of the Cromwellian past on the descendants of the original settlers. Yet in the years since the foundation of the state, the number of Protestants in the south had dwindled from 10 to 3 per cent of the total population. Most of those who left did so during the period described in The Story Of Lucy Gault, either frightened by IRA and vigilante attacks or unwilling to live in a state that would have a dominant Catholic ethos. In parts of County Cork, Protestants were subjected to a brutal campaign of sectarian violence. The ethnic cleansing of the Bandon Valley is one of the most odious chapters in our history, though I learned nothing about it at school. It took a Canadian academic, Peter Harte, to reveal the full savagery of the assault in his book The IRA And its Enemies.

Yet in the aftermath of the war Protestants would rise to the highest offices in the land. Our first President was a Protestant, and several government ministers as well as our greatest writer, W B Yeats. Once the civil war was over and the free state government established, the spectre of violent anti-Protestant agitation vanished. The cynic might say the South had no need of such tactics. The minority was so minor they posed no threat to the prevailing order. Yet Protestant influence on the development of Irish thought has been profound, out of all proportion to numbers.

The dissenting tradition represented by figures like Wolfe Tone and Robert Emmet, the intellectual questioning of Yeats and Sean O'Casey (a working class Dublin Protestant) ... and now, of course, William Trevor. By the end of William Trevor's novel, the heroine, Lucy Gault, has made a journey of personal reconciliation, but the novel suggests a larger journey to be undertaken on the island as a whole.

In this week, when Ulster is yet again threatened by the prospect of paramilitary violence, Mr Trevor's gentle telling of the events of the distant past reminds us of the terrible cost of division. I doubt that Johnny "Mad Dog" Adair or any of his extremist republican enemies will read Lucy Gault. What a pity. It might be the beginning of an education.

The writer is a BBC Special Correspondent