tuxedo
Dinner jackets? Still worn for quite a few things in the U.K.. As I remember, you're a Londoner which is probably different however in the 'gin and jaguar' belts of northern cities (even more in smaller affluent towns) they're still part of an affluent man's wardrobe.
Just buy a copy of Yorkshire Life, Cheshire Life, L*nca*shire Life, Lincolnshire Life, whatever, and the society' pages will be full of photos of local worthies wearing them.