I was listening to a rerun of the BBC panel game “My Word”. In his story, Frank Muir describes a t-shirt with the saying “Proofreaders Rule! O Q?” This got a moderate laugh from the audience, so they obviously got the joke.
I sure didn’t. I thought it might be related to some proofreader’s mark relating to a question mark (from the “Q”), but Googling on “proofreader question” didn’t turn anything up. Could someone please enlighten me?