No Wind of Blame (by Georgette Heyer)

(Amazon UK link) In my gradual re-reading of Georgette Heyer’s mid-20th century crime novels, I reached ‘No Wind of Blame’, which I first read in 2018. I had almost no memory of the book or any of the characters, other than a faint memory of how the crime was committed. 
The book is mainly set in a stately home owned by a flamboyant and very wealthy woman called Ermyntrude. She was widowed some years earlier, and then remarried the impoverished Wally Carter, who appears to have very few redeeming ...