You'll crucify Christ no longer in this town.
– James Larkin to the employers of Dublin

Strumpet City is the impossible Irish novel. The great master of the short story, Frank O'Connor, writing in 1942, claimed that it was simply not possible to write a social novel in Ireland. In Russia, he said, an author such as Chehkov could "write as easily of a princess as of a peasant girl or a merchant's daughter" but in Ireland "the moment a writer raises his eyes from the slums and cabins, he finds nothing but a vicious and ignorant middle-class, and for aristocracy the remnants of an English garrison, alien in religion and education. From such material he finds it almost impossible to create a picture of life . . . a realistic literature is clearly impossible."

O’Connor had a point. After James Joyce, 20th-century Irish fiction was generally defined by strategies for avoiding society. Writers withdrew into the small words of the short story (O’Connor and Sean O’Faolain), crafted novels from confined spaces or foreign destinations (Kate O’Brien), invented their own linguistic landscapes (Samuel Beckett) or turned the novel into a brilliant game (Flann O’Brien). They generally avoided history.

“History,” says Joyce’s Stephen Dedalus, “is a nightmare from which I am trying to awake.” What place could there be for the social and historical novel in 20th-century Irish fiction?

To say, therefore, that James Plunkett's Strumpet City , first published in 1969, is the greatest Irish historical novel is to risk damning it with faint praise. Ireland has no Walter Scott, no War and Peace . Plunkett may have learned from both, but he essentially had to invent the Irish epic for himself. To think of the most famous fictional depictions of Dublin is to be confronted with a brilliant minimalism: the tiny lives of Joyce's Dubliners ; the single day of Ulysses . Strumpet City unfolds over seven years. It deals not with isolated lives but with the way in which large events connect the most disparate of people. It encompasses a wide sweep of city life, from the destitution of Rashers Tierney to the precarious existence of Hennessy, the solid, aspirant respectability of Fitz and Mary, the priestly life of Fathers Giffley and O'Connor, and the upper-class world of Yearling and the Bradshaws.

Strumpet City does have a relationship to Joyce's Dubliners , a book that is an obvious influence on Plunkett's fine short-story collection The Trusting and the Maimed . But Plunkett also moves beyond that influence. Joyce saw Dubliners as an anatomy of the city as "the centre of paralysis". This might very well be a description of the city in the first part of Plunkett's epic. But in Plunkett's case the paralysis is convulsed by the shock of James Larkin's arrival.

We encounter the great labour leader first through the eyes (and ears) of Fitz: “At first, the accent was strange. Part Liverpool, part Irish, it produced immediate silence. The voice, flung back again from the high housefronts on the other side of the road, was the strongest Fitz had ever heard. From time to time the hands moved with an eloquence of their own.”

Larkin is, of course, a real figure, but Plunkett also had to imagine the subject of his epic for himself. If there was going to be a great, sweeping Irish historical novel of the 20th century, there was one event that overshadowed all others, that seemed ready-made in its dramatic power and symbolic scope: the Easter Rising of 1916. Plunkett chose instead a much more complex, and less famous, set of events: the Great Lockout of 1913.

The Lockout was, as Plunkett shows in Strumpet City , the culmination of five years of increasingly bitter disputes between Dublin's unskilled workers, organised by Larkin's Irish Transport & General Workers' Union, on the one side and the city's employers, led by William Martin Murphy, on the other.

Murphy eventually prompted 404 employers to demand that workers sign documents renouncing the ITGWU or be “locked out” of their jobs. (George Russell, at the time, described the employers as “blind Samsons pulling down the pillars of the social order”.)

The lockout of 20,000 workers lasted for more than six months before the ITGWU members and their families were effectively starved into submission. The conflict included violent police attacks on workers’ meetings and the formation, in reaction, of the Citizens’ Army. But, as Plunkett shows in a way that no documentary could ever capture, it was the slow violence of hunger, much of it directed against children, that was most telling.

Strumpet City is full of ordinary nobility – the stubborn pride of Rashers, the deep love between Mary and Fitz – and ordinary decency. Moments of unexpected kindness punctuate it. But the novel is, among others things, an anti-romantic portrait of a city mired in vicious poverty. In the period in which it unfolds, 1907 to 1914, a third of Dubliners were essentially destitute, living in single rooms in some of Europe's worst slums. These were often, in a grotesque irony, the grand former homes of the gentry. On one of the finest Georgian terraces, Henrietta Street, the 1911 census records an astonishing 835 people living in just 15 houses. One house alone, number 7, was shared by 104 people belonging to 19 families. Not surprisingly, diseases such as typhoid, tuberculosis and dysentery were rife: Dublin's death rate was 22 per 1,000 people; London's was 16. (From the beginning of Strumpet City , we meet death from disease: Sergeant Muldoon's young child dying of meningitis.) The city was notorious for high levels of public drunkenness and for the vast scale of its brothel district, Monto.

At the core of this poverty was Dublin’s failure to sustain a significant industrial base. In 1841, 33 per cent of the city’s workers were employed in manufacturing; by 1911, just 20 per cent were. There was a prosperous middle class working in the professions and administration, and a few thriving firms (Jacob’s biscuits, the Guinness brewery, the Jameson distillery) with steady employment for workers. But many people depended on casual labour as carters, on the docks or in construction. For every Fitz, with his job in the foundry, there were many Hennessys, picking up work wherever and whenever they could.

James Plunkett was rooted in the world of Strumpet City . He was born (as James Plunkett Kelly) in Dublin in 1920, just seven years after the Great Lockout and among people who had lived through it. He remembered, for example, that his mother had heard it rumoured that Larkin wore a wide-brimmed hat because he was the "anti-Christ and was obliged to hide a third eye that was in the centre of his forehead".

It seems significant that the area Plunkett was born in, Irishtown, is bounded by both the poorer district of Ringsend and the well-to-do suburb of Sandymount – hence, perhaps, the accuracy with which Plunkett captures both ends of the social spectrum in Strumpet City . Plunkett's father worked as a chauffeur and had served in the Great War – again, the confidence with which the novel evokes the Protestant and pro-British sides of the city's history surely owes much to direct experience. (Dublin's population, at the time the novel is set, was 15 per cent Protestant.) Plunkett, having left school at 17 for a job as a clerk at the Dublin Gas Company, actually worked for Larkin himself at the Irish Transport & General Workers' Union before he became a writer and then a radio and television producer with Radio Telifís Éireann.

Yet the strength of Strumpet City lies partly in the author's ability to hold his own feelings and ideals in check. Plunkett's politics were strongly socialist (he courted opprobrium in violently anti-communist Ireland by visiting the Soviet Union in 1955), sceptical of nationalism (it is striking that Strumpet City plays down militant nationalism, confining its expression largely to the old cook, Miss Gilchrist) and anti-clerical. Readers of Strumpet City will be in no doubt that the author's sympathies lie with the poor and with the workers' struggle for a better life.

But this is not a work of heroic propaganda. Plunkett infuses characters with whom he would not agree with vivid, detailed life. One of the finest portraits in the book, indeed, is that of the priggish Father O'Connor and his slow journey towards a fuller humanity – O'Connor is rich enough to be worth a novel to himself. This is why Strumpet City lives on as much more than a book "about" the Lockout. Asked to explain its success, Plunkett noted simply that "I didn't take my eye away from the people at any stage".

This is no boast: readers will find that the novel’s politics seldom exist outside of its superbly drawn people. And even though it is important that he gives his upper-class characters the same humanity as the poor workers, it is even more important that he gives complex life to people whose human dignity was, in reality, often denied.

At its heart, Strumpet City is a book of cast-offs. It makes itself out of forms and subjects that were largely cast out of Irish fiction. And it deals with cast-off people. Plunkett, in a Thomas Davis lecture on Larkin for Radio Éireann, noted that in the Dublin of the years leading up to the Lockout, the destitute "occupied the cast-off houses of the rich and they walked about – for the most part – in the cast-off clothes of the middle class." Children and the old searched the bins of the well-to-do for cinders, so that "even the fuel of the poor . . . was gathered through the same casting-off process."

This thought is taken up early in the novel itself, where, in a rare and discreet intervention of the authorial voice, Plunkett notes children searching bins for “half-burnt cinders”: “They came each morning from the crowded rooms in the cast-off houses of the Rich . . . The clothes they wore had been cast off by their parents, who had bought them as cast-offs in the second-hand shops.” In this imagery, there is the suggestion that the people themselves are cast-off humanity, discarded and of little value.

Strumpet City is, above all, a great defiance of this contempt for the poor. Its realism is not just a reflection of the way things were: it is also a statement of the way things should be, that attention must be paid to those whom history treats as the anonymous masses. We might give what he is doing the name of defiant realism.

Plunkett’s greatest creation, moreover, is a character who is at once the ultimate in harsh realism yet also poetic, even mystical.

Rashers Tierney, in lesser hands, could have been merely the embodiment of the horror of near absolute poverty. He is utterly destitute, despised and bullied by officialdom. He occupies the margins of life and of history, too poor even for the collective self-assertion of the workers. He is reduced almost to the level of his friend and equal Rusty, his beloved dog. He is King Lear’s “unaccommodated man . . . a poor, bare, forked animal”.

Yet Plunkett also allows him a dignity, even in this very identification with the animal world: “Anything that lived; men, women, children; dogs, pigeons, monkeys; even lesser things like cockroaches, flies and fleas, had to eat. He had been of their company long enough to sympathise with them all – the child rooting in the ashbin, the cat slinking along the gutter, the cockroach delicately questing along the wooden joins of the floor, its grey-blue body corrugated with anxiety. These were sometimes his competitors, but more often his brothers.”

In one sense Rashers is not a historical figure at all. He moves around and behind and beneath the history that is happening in the novel. He has always been there and he is still with us – in every one of the megaslums that are the fastest-growing kind of human habitation in the 21st century. There are countless millions of Rashers today, surviving on the edge of the wealthy world as scavengers on its cast-offs.

Strumpet City reminds us, among its great pleasures of vibrant narrative, that it is not so long ago since such people were part of the developed western world. And reminds us, through the power of vivid fiction, that they are not Them but Us: human, complex, worthy of dignity.

This is an edited version of Fintan O'Toole's introduction to the new Gill & Macmillan edition of Strumpet City . For details of One City One Book events, which take place throughout April, see dublinonecityonebook.ie .