This year marks the 600th anniversary of the construction of the ‘New Barn’ at Harmondsworth, the largest surviving medieval timber-framed barn in England. To celebrate this remarkable example of medieval architecture, English Heritage and the Friends of the Great Barn at Harmondsworth are hosting a conference in the Barn and the adjacent church of St Mary on 5 September 2026. The in-person ticket price includes a full day of talks, tea and coffee, a light lunch, and a drinks reception. There will be opportunities throughout the day to visit the Barn. 

Described by the former Poet Laureate, John Betjeman, as ‘a cathedral’, Harmondsworth Barn was built in 1426. All those who now visit it are, like Betjeman, struck by the size, proportions and atmosphere of this magnificent structure, even though it was not designed as polite architecture. Its function was to store the agricultural produce from the manor.  Today the Barn’s significance lies in its extraordinary scale (over 58 metres/190 feet long), the near-complete survival of its medieval structural timbers, its precocious features, and the exceptional survival of documentary evidence relating to its construction, ownership and use.

This conference aims to act as a catalyst for new research into medieval vernacular buildings, using Harmondsworth Barn as both case study and inspiration. The conference will include papers on the Barn’s ownership and use, construction and materials, recent archaeological investigations and repairs, and on the changing local cultural, economic and environmental context.

The programme will include the following papers:

• Julian Munby: Harmondsworth, Heath Row and the Measured Mile
• Robert Cowie: Buildings and fields: an archaeologist’s view of Harmondsworth’s medieval landscape
• Ruth Siddall: London ferricrete and the geology of Harmondsworth Great Barn
• Duncan Berryman: Construction materials of barns in the later Middle Ages
• Peter McCurdy: The mysteries of Harmondsworth Barn: the 1980s repairs
• Ptolemy Dean: Repairs to the Barn in 2014
• Justine Bayley: What Now? Ongoing research and questions for the future
• Paul Reed: Practical demonstration of how the medieval master would likely have made a measuring rod
• Edward Impey: Keynote lecture
• Michael Stansfield: William of Wykeham and Harmondsworth
• Nick Holder: William of Wykeham's other medieval barn: Prior's Hall Barn, Widdington, Essex
• John Purser: Local agriculture and its demise
• Tom Nickson & Jessica Barker: Harmondsworth Barn and the environment in the Middle Ages
• Abigail Longmate: A rural stage-set: Repurposing barns as theatres in the twentieth century

Book tickets for the conference

The Barn will be open from 9.15am. Tea and coffee will be available in St Mary's Church Hall from 9.15am. The conference will begin in St Mary's Church at 9.45am and will finish around 5pm, followed by a drinks reception.

With support from the Paul Mellon Centre for Studies in British Art.