Thorne is situated to the east of an unclassified road 250m down from the B4319 at Merrion towards Trenorgan. It is on the edge of the Royal Artillery Corps Castlemartin Range. Thorne appears to have been the farmhouse of a small independent agricultural holding of about 32.4 hectares, later absorbed into the Stackpole Estate. The walls are of limestone rubble in mortar of various mixes of clay and lime, rendered or limewashed. The chimneys are of masonry, and the roofs now of slate or corrugated iron, were formerly partly thatched. The house is aligned north-east south-west, with the site sloping slightly to the south- east. The older part is a two-storey three-unit house in coursed rubble masonry consisting of a kitchen at the east, hall and parlour. Within this part, the hall and part of the parlour, but not the cross-wall east of the hall, are thought to be the oldest. The building has two large buttresses at the south side. There are opposed lateral entrances into the kitchen, the one at the north being through an equilateral pointed and chamfered arch. There is a very large east end chimney with ovens. The chimney has sloping flanks and a pyramidal cap above the cornice band. All windows are 20th century stained wood. The hall and parlour were used as farm storage until recent extensive renovations (c.1990). The hall was then described as open to the roof and is now still open to the roof apart from new stairs and a gallery. There has been an upper floor in this room, but not originally. What is taken to be an outshut at the north (or a survival of an earlier wall) combines the original stairs to the upper floor of the parlour unit, a lateral chimney in the hall, and also the porch giving access to the kitchen (though the porch is later). The hall chimney in this outshut has a tall tapering square stack with weatherings to the cornice and offset on its west side. The cross-wall east of the hall contains a stone Tudor arch and a niche with an ogee head. This wall does not appear to be as early as the other walls of the hall. The hall roof has been rebuilt (c.1990) in imitation of the roof removed in the recent renovations. This includes a truss at the west end of the hall incorporating timbers which carry two purlins and which curve inwards at the foot in the manner of crucks (a rare feature, but known in Pembrokeshire, south-west Devon and Cornwall). They bear on corbels, which may not be original, about 0.5 m below the level of the present south wallplate. The principals of the hall roof have lap-jointed collar beams. Photographs of the original timbers suggest these details are correctly imitated. There are two incised dates. The first has the letters IM and the date 1679 appear (in dissimilar styles of character) on a side beam of the original east end hearth (this timber may not be in situ). The same initials and the date 1726 appear centrally on the side of a first-floor beam in a part of the house added to the earlier structure at the east. There may be a connection with an owner or owners of the surname Moody. The owner c.1782 appears to have been named Moody. It was listed as a mediaeval hall house of regional type but with unusual constructional detail. It is a farmhouse with an extremely complicated development, incorporating a number of local traditional details, and probably late mediaeval.
(Source: CADW listed buildings database, 8 February 1996; NMR Site files, AJ Parkinson, 7 September 1979)
Ian Archer, RCAHMW, 17th March 2005