Haverfordwest Priory, dedicated to SS. Mary and Thomas the Martyr, was founded by Robert FitzRichard around the year 1200 on the outskirts of the important mercantile town of Haverfordwest, a position which ideally suited the Augustinian Order. Despite the unstable location of the site, the ground of which needed to be raised and provided with considerable drainage due to regular flooding, the priory flourished until the sixteenth century.
There are substantial remains of a thirteenth century cruciform church, together with cloisters and claustral ranges which were redeveloped in the fifteenth century, and a tower dating to that later period. The largely intact remains of the medieval Priory Garden (NPRN 79037) were discovered through excavation.
Haverfordwest Priory appears little in the historical record, having avoided all major upheavals, and being spared from such fires or attacks which brought attention to other similar institutions. Following the dissolution of the monasteries in 1536 the site passed into private ownership, including that of Sir John Perot, who furthered the ruination of the buildings, using stone from the Priory to repair his home at Haroldson. Following this the site remained largely unused and neglected until 1982 when the Guild of Freemen of Haverfordwest gave it into State care, and there followed extensive excavation and conservation works.

Source: Rees, Sian E. 1999. Haverfordwest Priory: Cadw Guide

K. Steele, RCAHMW, 7 November