valuer

The Enfield oak was worth £1m, according to tree valuer Russell Miller, who made his estimate using the Capital Asset Value for Amenity Trees system.

The Department for Housing told the BBC it had "consulted lenders" on spray foam insulation, and it would "rely on the views of valuers and surveyors on this issue".

A government spokesperson said it had "consulted lenders about this matter who say they rely on the views of valuers and surveyors on this issue".

Auctioneer and valuer James Warren said he thought the seller would be "fairly happy" with £21,000.

"He's got a wonderful archive of Christmas and greetings cards, drawings of the cat, all from David Hockney's time in Bradford," the valuer said.