English Heritage marks the barn's 600th year with 14 papers on Saturday 5 September. Tickets are £25, £20 for students and members, and the day streams online.

The largest surviving medieval timber-framed barn in England turns 600 this year, and the anniversary is being marked on Saturday. English Heritage and the Friends of the Great Barn at Harmondsworth are running a full day of talks in the barn and the church next door, on 5 September, from 9.15am to 5pm.

Tickets are £25 for adults and £20 for students and English Heritage members, in person or as an online stream. (Harmondsworth Barn 600th Anniversary Conference, English Heritage)

Harmondsworth sits on Heathrow’s northern edge, roughly five miles south of Uxbridge. The barn is normally free to get into, and it will be free again on three days later this month. Saturday is the exception, and it is the one day of the year when the people who have measured, dated and repaired the building are all in the same room.

What the ticket buys

The price covers a full day of papers, tea and coffee, a light lunch and a drinks reception at the end. There are chances to go into the barn itself during the day. The event is listed as suitable for adults.

The running order:

  • 9.15am: the barn opens, with tea and coffee in St Mary’s Church Hall
  • 9.45am: the conference starts in St Mary’s Church
  • around 5pm: the last paper finishes, followed by a drinks reception

Fourteen papers are on the programme. English Heritage says the aim is to “act as a catalyst for new research into medieval vernacular buildings”, using the barn as both case study and inspiration. Among them:

  • Julian Munby: Harmondsworth, Heath Row and the Measured Mile
  • Robert Cowie: an archaeologist’s view of Harmondsworth’s medieval landscape
  • Vivien Ainley: Timber for the Barn: Why Kingston?
  • Peter McCurdy: the mysteries of Harmondsworth Barn, and the 1980s repairs
  • Jeremy Ashbee and Justine Bayley: the philosophy and practice of the 2014 repairs
  • Paul Reed: a practical demonstration of how a medieval master would have made a measuring rod
  • Michael Stansfield: William of Wykeham and Harmondsworth
  • Abigail Longmate: repurposing barns as theatres in the 20th century

The conference has support from the Paul Mellon Centre for Studies in British Art.

Why 1426 matters

The barn was built in 1426 by Winchester College, as part of its manor farm at Harmondsworth. It is Grade I listed, which English Heritage says puts it alongside the Houses of Parliament and Westminster Abbey for architectural and historic interest. The former Poet Laureate John Betjeman called it “a cathedral”, and the nickname Cathedral of Middlesex stuck. (Harmondsworth Barn, English Heritage)

The numbers explain why. The barn runs over 58 metres, or 190 feet, and is about 12 metres wide and 11 metres tall. Thirteen oak trusses hold up the roof. It has a nave and two aisles, which is what gives it the proportions of a church rather than a farm building.

What makes it useful to historians is not only the timber. English Heritage points to the near-complete survival of the medieval structural members alongside an exceptional written record of who built it, who owned it and what it was used for. Most medieval barns have one or the other. This one has both.

Three free days this month

If Saturday is not for you, the barn opens free three more times in September, for Heritage Open Days and London Open House:

  • Saturday 12 September, 11am to 5pm
  • Sunday 13 September, 11am to 5pm
  • Sunday 20 September, 11am to 5pm

After that it returns to its normal pattern: 11am to 4pm on the second and fourth Sundays of the month, running to 25 October. Entry is free.

Chart of when the Great Barn at Harmondsworth is open in September and October 2026: the ticketed 600th anniversary conference on 5 September from 9.15am to 5pm; free Heritage Open Days and Open House days on 12, 13 and 20 September from 11am to 5pm; and normal free opening on the second and fourth Sundays until 25 October, 11am to 4pm
Only one date this autumn is ticketed. Everything else is free.

Our round-up of the council’s own Open House line-up covered six borough sites. The barn is not one of them, because it is English Heritage’s rather than the council’s, so it is a seventh free opening that the council’s announcement did not mention.

Getting in, and getting there

The address is The Great Barn, Manor Court, High Street, Harmondsworth, UB7 0AQ. English Heritage has these practical notes:

  • Parking: a free English Heritage car park at the rear of the barn
  • Finding it: take the small spur road off High Street, to the right of The Five Bells pub. St Mary’s Church is then on your right, and the barn is through the gate at the end
  • Access: the barn is accessible for wheelchair users
  • Facilities: none on site, and there are no public toilets in the village. The church hall has toilets for part of Sunday mornings when the church is open, and there are two pubs within 200 metres
  • Dogs: assistance dogs only
  • Groups: the barn can be opened by arrangement for schools and other groups, on 020 8759 1874

What it means for you: if you want the conference, book before Saturday, because it is ticketed and the online stream is the fallback. If you only want to see the barn, do nothing and turn up on 12, 13 or 20 September, when it is open longer than usual and costs nothing. Both options are close to the Elizabeth line at West Drayton; overnight closures and other travel changes are on our roadworks and travel page.

Where the Heathrow expansion process stands, and what it means for the villages on the airport’s northern edge, is tracked on our Uxbridge planning news page.

Sources