The timber-framed Harmondsworth Great Barn in west London was built in 1426-27 and is one of the least altered medieval buildings in Britain. It is Grade I listed and along with Stonehenge and Hadrian’s Wall, it is part of the National Heritage Collection, in the care of the charity English Heritage.

A third runway at Heathrow Airport will have a major impact on Harmondsworth Great Barn and cause irreparable harm to its setting. For the future of this medieval masterpiece – dubbed by Sir John Betjeman as the “Cathedral of Middlesex” – today’s decision is a deeply disappointing one. English Heritage will look at the implications of this decision and what steps might be put in place to limit – as far as possible – the damage to the barn.