In the seventh century an Irish monk called Muirchú moccu Machtheni composed his Life of St Patrick from which derives much of our knowledge about the latter. Muirchú’s work was very much a hagiography and ought not necessarily be taken as historically accurate. For example, he tells a story of Patrick coming to the Hill of Slane in County Meath and lighting a Paschal fire there in the year 433. This act was in defiance of orders issued by the High King Laoire who forbade any other fires being lit while that on the Hill of Tara (some ten miles from Slane) burned to mark the pagan Spring festival of Beltaine. According to Muirchú King Laoire, although angry, was sufficiently impressed by Patrick’s bold non-compliance that he allowed him to continue proselytizing. The same source also proposes that one of the king’s druids called Erc was even more affected by what had occurred and converted to Christianity, after which he was made Bishop of Slane by Patrick. Later moving to Kerry, Erc is said to have been the teacher of St Brendan, the sixth century ‘Voyager.’

Although a religious house was established on the Hill of Slane, the present remains date from a later foundation created for the Franciscan order by the Flemings, a prominent Norman family, members of which were Barons Slane from 1370 until the death of the last of the direct line some four centuries later. Like many others, the Flemings remained loyal to the Roman Catholic faith and suffered the consequences: Christopher, twenty-second Lord Slane was attainted in 1691 owing to his support of James II and subsequently moved to mainland Europe. He was eventually reconciled to the British government and in 1713 Queen Anne created him first Viscount Longford, but since no letters patent were issued before her death a year later the title had no validity (in any case, he in turn died without male heirs in 1726). Meanwhile the Franciscans saw their friary closed in the 16th century but then temporarily restored to them by the Flemings. Members of the Capuchin order also took up residence here at one stage but the site seems to have been abandoned for good in 1723, after which it fell into ruin.

What can be seen today on the Hill of Slane is primarily a rebuilding of the friary undertaken for the Franciscans in 1512 by Christopher Fleming, fourteenth Lord Slane. It is divided into two sections: the church and the college. The former is surrounded by a walled graveyard and its most striking feature is the tower at the west end of the building. This rises some sixty-two feet and incorporates a fine 15th century Gothic window above the doorcase. Relatively little remains of the main body of the church. The adjacent college buildings were intended to house four priests, four lay brothers and four choristers, with three ranges grouped around a central courtyard and the fourth side to the west closed by a curtain wall. A spiral staircase in one corner provides access to the upper levels, the views from which explain why this location was always likely to be of significance; from here it is possible to scan the surrounding countryside for several miles to south and east. Nearby are the remains of a motte and bailey believed to have been constructed by the Flemings before they moved their residence to a lower site which is the present Slane Castle.