Travellers simply have to arrive at a National Trust property with a flight ticket from the affected period together with their passport.
The offer will run as long as people remain stuck in the UK, giving travellers the chance to visit some of the other places they may not have had time to enjoy.
Fiona Reynolds, Director General of the National Trust, said: “British travellers stranded overseas have been shown tremendous hospitality by their hosts.
“This offer is a way of reciprocating that kindness and saying thank you on behalf of the country.”
Graham Deans, Assistant Director for Operations in the Trust’s Thames & Solent Region, said: “It’s the perfect time to visit Osterley and it’s just down the road from Heathrow from anyone stranded or staying near there.
“It’s a great spot to get away from everything, so we hope some visitors will be able to take up the chance to visit whilst they’re here.”
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