One of them holds Lord Edward Fitzgerald, the United Irishman who died in 1798 from wounds sustained during his arrest. The man who arrested him, Major Sirr, is buried a few metres away in the churchyard outside. That proximity, unplanned and unannounced, is the kind of detail that rewards a slow look around a building that most of the city walks past without noticing.

The site has been a place of Christian worship since at least 1179, when a medieval parish church here was recorded as the property of the Holy Trinity Priory. That earlier building was destroyed by fire in 1311, and the church that replaced it went through repeated rounds of enlargement and repair. Timber was carted from Castleknock and Drimnagh, or brought by ship from Wexford in Elizabethan times; slates arrived by water to Dublin quay and were weighed at the city crane. The medieval church had two freestanding chapels, one to the north and one to the south of the chancel, and the northern one gave its name to St Martin's Lane, a passageway between the church and Castle Street that vanished only in the eighteenth century. By 1715 the building was being substantially rebuilt, attributed to Colonel Thomas Burgh, who also designed the library at Trinity College. An octagonal tower followed in 1729 and a wooden dome in 1731, but a fire on 9th November 1754 took the roof, dome, organ, pews and galleries, reigniting three days later. The church we see today is largely the product of that rebuilding, reopened in 1759. The craftsmen involved are recorded by name: Thomas Tunney as plasterer, Andrew Goodwin for the oak woodwork, Michael Maguire for the stucco in the chancel. A 160-foot tower and spire were added in 1768 and subsequently demolished, which Wheeler and Craig, writing in 1948, called one of the most lamentable losses in Dublin's architectural record.

The church is on Werburgh Street, close to Dublin Castle, and is not always open to casual visitors, so it is worth checking ahead. Those who do get inside will find the Viceregal pew at the west end, with a carved royal arms in relief dating from 1767 and two crowns on brass posts. In the porch sits the Purcell double tomb, a late Gothic chest tomb dating from roughly 1500 to 1520, originally in the demolished church of St Mary del Dam and moved here in the late sixteenth or early seventeenth century. The male effigy is in full plate armour; the female wears a pleated gown belted with rosettes. The side panels carry a dense population of saints and ecclesiastical figures. Elsewhere in the interior, the recumbent tomb of the sixth or seventh Earl of Kildare, rescued from a wall in 1914, lies near monuments gathered in from two other demolished Dublin churches, St John's on Fishamble Street and St Bride's. The pulpit, carved by Stewart to a Francis Johnston Gothic design, came from St John's in 1877 and had itself originated in the Chapel Royal.