femmenoire@19: This Yank first heard of it in an Agatha Christie story so you're probably right!
...no wait. The Agatha Christie story involved "all my eye and Betty Martin." Well I don't know remember where I first heard of 19ac but it is UK (even the initialized version isn't in use here).
Fantastic puzzle, my CoD might be 1ac (also FOI) because the surface works so well. LOI were 22ac and then 23d--took me a while to remember the expression in 22ac.