Not ZSL, but on Friday visited Bentley Priory Museum, RAF Strike Command, near Stanmore. Their website still suggested that masks should be worn. When I arrived the chap selling the tickets and the chap welcoming you and guiding you (ex RAF chaps it seems) both proudly wore blue masks - but was unhooked when he spoke to me as he could see I had hearing aids. But nobody else did, none of the (relatively few) visitors or any of the cafe staff and not a word was mentioned about them. It seemed totally for show, to be seen doing what 'they' considered their 'duty'.