Means you look properly daft and embarrassed because you got something wrong, usually in public. Like you’ve metaphorically face-planted into an omelette and everyone saw it happen. Used when someone’s big confident moment backfires, or when a smug claim gets instantly proved wrong. Brutal, classic, and weirdly satisfying to say.
"You told everyone the train was cancelled, yeah? Now it’s rolling in and the whole platform’s staring. Nice one, mate, proper egg on your face"