The tithe barn at Headstone Manor is part of a moated manor complex, very similar to the one at Manor Farm in Ruislip. The barns however are quite different. The Headstone Manor barn is about 45 metres long with ten bays and two wagon porches. It the main barn has a clear span of about 8metres and there are no aisles.
With changes in farming methods and increased residential development in the area, the barn fell out of use and decayed. In 1943 it was repaired and became The Barn Theatre. In the 1970s a major restoration programme was carried out by the London Borough of Harrow and it is now part of the Harrow Museum and Heritage Centre.