St Mary'S House

St Mary's House is a public building, now a house, dating from the 15th century. It has been altered in the 16th, 18th, and 19th centuries. The building is timber framed and plastered, with a roof covered in handmade red plain tiles. It consists of a two-bay range facing southwest, with a two-bay crosswing to the right, now fully incorporated into a continuous roofline. A 16th-century external stack is located at the rear of the left bay, with the upper portion rebuilt around 1985. An 18th-century external stack is situated to the right of the crosswing. A 19th-century single-story wing extends to the rear of the main range, clad in weatherboard and roofed with slate.

The building has two stories and attics. The front elevation features two early 19th-century sash windows of 12 lights, and a central splayed bay with sashes of 2-6-2 lights. A central six-panel door is present, along with a fanlight with radial tracery, which is now blocked or painted over. A portico with two plain columns and two engaged Corinthian columns is also a feature. The central bay projects forward and is gabled, creating a symmetrical appearance.

The rear elevation includes an early 19th-century half-glazed door with 12 lights and a tripartite sash window of 4-12-4 lights, both with crown glass. A continuous jetty runs along the front, underbuilt and supported by plain brackets. The ground floor appears to have originally been a large, undivided space; a moulded binding beam is found in the crosswing, while deeply chamfered beams are present elsewhere. The left room has a wide wood-burning hearth with a chamfered mantel beam spanning one bay, originally reduced for a Victorian cast iron grate. Early 19th-century cupboards are set into the window reveals. The early 19th-century staircase features scrolled tread-ends, a turned newel with an acorn finial, stick balusters, a wreathed handrail, and a similar gallery. The lower storey is 2.51 metres high. The building includes jowled posts and edge-halved and bridled scarf joints in each wallplate of the crosswing. Original studded partitions are found on the first floor, dividing it into three rooms. Late 16th-century inserted ceilings feature chamfered beams with lamb's tongue stops. The main range has a crownpost roof, from which the axial bracing has been removed; the crownpost is octagonal, with step stops on a cambered tiebeam.

The originally open ground floor and its prominent location facing the road from London suggest that the building may have been constructed as a market hall for the Abbot of Westminster, later converted to domestic use after the Dissolution.