As part of a grant aided programme of consolidation works to the building variously known as Minsmere Chapel, Leiston Chapel or Old Abbey Chapel, English Heritage required that archaeological recording and interpretation would be undertaken as an integral part of the project. The site, which lies within the coastal marshes now occupied by a RSPB bird reserve, was that of the original Premonstratensian Abbey at Leiston built by Ralph de Glanville in about 1182 with a dedication to St. Mary de Insula. Due to increasing inundation by the sea, in 1363 a new abbey complex was built by Robert de Ufford at a site further in land. However, documentary evidence suggests that a presence was maintained at the old site until the dissolution in 1537 and the building on the site is the only surviving evidence of this continuing occupation. Aerial photographs and geophysical survey also suggest that the building was constructed within the body of the original abbey church that itself lay immediately south of a cloister.
Three main phases of construction were recognised. The first, represented by the lower sections of the standing walls, included evidence for three contemporary windows, a doorway and an enigmatic internal niche. This initial phase was thought to date to soon after the abandonment of the abbey in 1363. The second phase was represented by the upper sections of the walls with their characteristic use of brick, evidence of two additional windows and the blocking of the earlier Phase I windows. This phase has tentatively been associated with John Green who, after retiring as Abbot of the abbey at the new site in 1527, lived out his years as a consecrated anchorite at the chapel. The third phase involved the insertion of a World War II pillbox into the eastern end of the structure which utilised the existing architectural openings.