Ah yes: Gourmet Night at Fawlty Towers:
'I should have never let you write that advert,' says poor Sybil to her husband Basil, in the classic sitcom. 'Fancy putting "No riffraff." '
But as Basil explains:
'When you're presenting haute cuisine, you don't want the working classes sticking its nose in it.'
My Collins dictionary defines riffraff as worthless people, especially collectively. The Concise Oxford Dictionary says disreputable or undesirable people (and spells it riff-raff).
I'd have great trouble spotting a worthless person, but being disreputable seems to be almost a necessity nowadays for anyone famous.
Well, they can be spotted very easily indeed: undesirable probably covers half our relations and most of our colleagues, for a start.
If I really wanted to see a lot of undesirables, though, I might try a Gourmet Night dinner at a small hotel on the English South Coast.
Mind you, I doubt they'd let me in.
Spot the frippet: riffraff. This word comes from the Old French rif et raf, which meant one and all, or every bit. It's related to rifler to plunder and rafle a sweeping up.