Planning began in 1920 to replace the older Cathedral of the Immaculate Conception. By 1933, Bishop Thomas Mulvany was laying the foundation stone of something altogether grander: a basilica-form cathedral in Renaissance Revival style, designed by William Byrne & Sons of Dublin, faced in granite hauled from the Barnacullia quarries above Dublin. Twin towers rose to 55 metres, crowned with bronze crosses. The seating capacity was 5,000, an enormous number for a town that then had only a few thousand inhabitants. When it opened on 6 September 1936, at the specific request of Pope Pius XI, it became the first cathedral in the world to be dedicated to Christ the King — a feast the Pope had instituted only a decade earlier. The total cost was £275,000, a staggering sum for a parish in 1930s Ireland, raised across years of collections and emigrant donations.

The mosaics in the side chapels were the work of Boris Anrep, a Russian-born artist who had become one of Europe's foremost mosaicists. His work covers the floors of the National Gallery in London and the chapels of Westminster Cathedral. In Mullingar he was given two chapels: one for Saint Patrick, one for Saint Anne. The Saint Patrick mosaic shows the saint at the moment of his greatest defiance, lighting the Paschal fire on the Hill of Slane against the king's order. Patrick lifts the cross in one hand and grips a torch in the other; the firewood at his feet has been arranged in the shape of a Christogram, the symbol he was about to plant in Irish soil. It is a piece of pure narrative drama in coloured glass.

The Saint Anne mosaic is something else. Anrep had met Anna Akhmatova in Saint Petersburg before the First World War, and during the war they had a brief, intense affair. He left Russia just before the Bolsheviks took power. She stayed, became one of the great poets of the twentieth century, was persecuted by Stalin, watched her son sent to the camps. They never saw each other again. They never even corresponded for forty-eight years. But Akhmatova haunted Anrep's imagination, and her face appeared again and again in his mosaics across Europe. Mullingar is the only one of them to give her name — spelled Anna in the Russian way, hidden in plain sight inside an Irish cathedral. She, for her part, wrote some thirty-four poems about him. It is the kind of secret a small town can keep without quite knowing it has one.

Today the cathedral still dominates Mullingar's skyline beside the Royal Canal, those twin towers visible from kilometres out across the lowland Westmeath countryside. The seating capacity is rarely tested any more — Ireland's vocations crisis and the long erosion of regular Mass attendance have left this building, like so many built in its era, larger than it needs to be. But the mosaics endure, more visited now perhaps for their story than for their devotion. The cathedral remains the principal church of the Diocese of Meath, and it was solemnly consecrated on 13 August 1939, three weeks before the world went to war again.

Visitors come down Mary Street and find the cathedral set back from the road behind a small forecourt. Inside, the nave is high and bright, the granite walls catching the light from the clerestory windows. The Saint Anne chapel is to one side, modest in scale, easy to miss. Stand in front of the mosaic and look at the saint's face — long oval, dark eyes, the slight asymmetry of a real human likeness rather than an idealised holy figure. The script reads "Anna." Then walk back out into the Westmeath drizzle and consider that a Russian poet, a Bavarian-trained Russian artist, an Irish bishop, and an English mosaic firm all conspired across one of the most violent decades in European history to put a memorial to lost love into a midlands cathedral. Few buildings carry quite so unlikely a story.