The number he repeats in almost every chapter is that in 1955 a country house was coming down every two-and-a-half days. Lots of reasons; land wealth hadn't been reliable wealth since the 1870s, and the combined effects of two world wars - death duties in WWI, casual destruction when the buildings were requisitioned during WWII, and (this is my interpolation) there was an enormous disinterest in old stuff during the 1950s and 1960s, even among the few remaining owners who could afford to maintain the places.
What seems such a waste, looking at a photo of high, arched, coffered ceilings over a floor covered with broken wall-moldings and sofa stuffing, is not that the original owners couldn't afford it any more - as families go, the English rural rich seem to have had a good long run - but that all the original work to make the places was wasted. Firewood can't be the right use of a Grinling Gibbons carving; even during the war, it's hard to believe that its sale price as architectural salvage wouldn't have brought a little more coal over from the States. (But maybe there wasn't any spare shipping tonnage, and besides, bored scared troops barracked in a ballroom are very likely not thinking that far ahead. Nor could they provide provenance.)
Apparently he's all in favor of turning these buildings into flats or
retirement homes or anything that will keep enough of them up to leave
historical evidence. I bet the plumbing arrangements are deeply creative.
So wrote clew in
History (20th c.).