From the middle of the 17th century the castle appears to have gone into ruin, and in 1729 Archbishop Hoadly decided to demolish all of the structure except one tower, and this tower still stands as part of the Priory. In place of the castle he built an archiepiscopal house.
The last of the archbishops to reside at Tallaght was Lord John Beresford, who found the house so dilapidated that he had an act of parliament passed in 1821, ridding the Sea of Dublin of the responsibility of maintaining a country seat. In the following year Archbishop Magee leased the property to Major Palmer, Inspector General of Irish Prisons, on condition that he demolish the house, lest it ever became a monastery. Palmer dismantled all but the mediaeval tower, and from the materials built himself a house where the retreat house now stands. The demesne then passed to Sir John Lentaigne, and he sold it to the Dominicans in 1856.
The first Dominicans settled in Ireland in 1224, and soon the Order spread throughout the country to establish houses in all the principal towns and cities. Three times during the turbulent and troubled history of Ireland – in the 16th, 17th and 18th centuries – the Dominicans in Ireland were uprooted, hounded, hanged, banished and imprisoned. By God’s grace, however, the Order survived, and the founding of Tallaght was a milestone in its revival. Since the penal days the friars had to seek their training and education overseas, and one of the centres in which they had found refuge was the priory of Corpo Santo in Lisbon, which had been founded by Irish Dominicans in 1615. A portion of the Lisbon College was sold in 1856 and the proceeds of the sale were used to found Tallaght.
The first friars lived in Major Palmer’s house (now incorporated in the retreat house). They were Fathers Thomas Mullins, Thomas Rush and Thomas Burke, the renowned preacher. Their choir was in the ground-floor of the mediaeval tower. In May 1864 Fr Goodman, the Provincial, laid the foundation stone of the priory. Cardinal McCabe laid the foundation stone of the church in October 1882, and it was dedicated to ‘The Immaculate Virgin Mary of the Rosary’ by Archbishop Walsh in October 1886, as a memorial to Fr Tom Burke, who had died three years before, and lies buried in the cloister there. It was a fitting memorial to one whom his contemporaries had acclaimed as the greatest preacher in the English-speaking world, and whose zeal for full Dominican observance is still an inspiration. The wing connecting the church and tower was completed in 1903. Another wing and a library block were completed in 1958. The latter is now the headquarters of the Priory Institute and Distance Learning Programme (www.prioryinstitute.com).