EARLY HISTORY
All Saints’ Church, Mullingar, was first referred to in a charter of 1192–1202, which noted that the church had been given to the Augustinian priory of Llanthony Prima in Wales by Simon de Rochford, Bishop of Meath. The prior of the abbey became rector of Mullingar and was responsible for appointing priests. The link with Llanthony was retained until 1540, during the Dissolution of the Monasteries in the reign of Henry VIII.
IMAGE: 1. Llanthony Priory

In 1172, Henry II of England granted the kingdom of Meath to Hugh de Lacy, who in turn granted William le Petit the Barony of Magheradernan. Mullingar became the territory’s main stronghold and the location of Petit’s castle. In a communication to Llanthony dated circa 1202–1210, the dedication of the church to All Saints was confirmed by Petit. He stipulated that there would be two chaplains and a deacon attached to the church of Mullingar, who were to say mass in the chapel of his castle when he or his wife were in residence.
IMAGE: 2. Early-medieval church

The local tradition that St. Mary’s Augustinian Priory was located on the site of All Saints has no apparent basis in fact. The medieval parish church predates the priory, which was founded in 1227. It is very unlikely that the two structures shared the same site. The precise site of the monastery is not known, but Sir Henry Piers, writing in 1642, noted that it stood at the east end of Mullingar.