From 1506 until 1928 The Great Barn was a working farm building. By the time it was built, Headstone Manor had been a residence of the Archbishops of Canterbury for over 150 years, but the farm had been here since at least the 11th Century.

Archbishop William Wareham commissioned The Great Barn from a local carpenter. Its magnificent oak frame was constructed from trees felled from the ancient woodlands on the site.

In 1546, Archbishop Thomas Cranmer surrendered Headstone Manor to Henry VIII, a consequence of the beginnings of the Reformation. Henry sold Headstone on to Lord Edward North, whose descendants remained landlords for another 200 years.

The Great Barn was originally configured as a seven-bay threshing barn (three bays either side of the wagon porch nearest the moat). There were an additional three bays and a second wagon porch to the south to provide stabling. Threshing barns vary in size, but always have an odd number of bays. The wagon porch and through doors opposite formed the central bay needed for access and ventilation during the threshing process.

A lease issued in 1514 defined The Great Barn as shared between the Archbishop and the lessee, Robert Marsh. A timber partition separated the three bays and the wagon porch at the west end for the Archbishop’s use (for his horses, hay, fodder and carriages). The socket holes for this partition are still visible in the frame of the third bay.

In 1894 The Great Barn became home to the cows of Hall & Sons Dairy. The Halls were the last farmers at Headstone, but they moved their entire dairy business to Pinner Park Farm in 1928, when Headstone’s remaining fields were purchased to provide a public park amidst the ever-expanding housing developments of the time.

The Great Barn found a new lease of life during The Second World War, first as a training venue and stores for the Home Guard, and then as a theatre for the local authorities’ ‘Holiday-at-Home’ campaign.

In 1986, after decades of work by local volunteers The Great Barn was opened as Harrow Museum & Heritage Centre. Now, the whole site has been revitalized as Headstone Manor & Museum, with The Great Barn providing a wonderfully historic space for events.