Formal-Informal
Staff job at Bentley Priory in the early 90s: The whole office gets invites from the Gp Capt to dinner with him and Mrs Gp Capt. "...Dress: informal..."
After diverse discussions, I was deputed to ask him exactly what this meant.
He leant across to the bookshelf and took out his copy of Debrettes and said: "Formal is Dinner Suit so informal is obviously lounge suits" -and so it was, much to all our wives' amazement.