Chapel of St Mary, Approximately 150 Metres North West of Thame Park House

The Chapel of St Mary, located approximately 150 metres northwest of Thame Park House, is an early 14th-century chapel that was remodeled around 1836 by D. Harris and R. Abrahao for Sophia, Baroness Wenman. The building is constructed of coursed stone rubble, with lined render on the stone rubble west front and a stone slate roof. It features a two-bay nave and chancel plan.

The west front has a central plank double door set within a two-centred moulded doorway that has a gabled surround topped with a cross finial. There is a 19th-century three-light window with Geometrical tracery and a hood mould above it. The chapel has angle buttresses on both sides and a battlemented parapet at the gable, which is crowned with an octagonal bellcote.

On the south front, there is a blocked 14th-century doorway to the left with a hood mould, and to the right, a 19th-century two-light window with geometrical tracery and a hood mould. The roof features a parapet with quatrefoil panels.

Inside, the nave has a 19th-century ceiling of four bays in the Perpendicular style, while the chancel has a sexpartite vault with ribs that spring from the left and corbels. The chancel floor is laid with 15th-century floor tiles, and there is a four-centred chancel arch. The nave floor contains some re-set 17th and 18th-century memorial slabs. The chapel is furnished with 19th-century pews, box pews, and a pulpit with a reading desk, along with a 19th-century stone font supported by cluster columns. A wall monument by Westmacott commemorates Philip, the 7th Lord Wenman. Historically, the chapel was likely built outside the gates by the Abbey as a chapel for travelers.