"You are [name], and I claim my £5"?

Where does this phrase come from?

I usually see it on blog comments when someone is accused of sounding like someone famous.

e.g.

Post 1: “I hate mooses”
Post 2: “You are Sarah Palin, and I claim my $5”

I don’t know if it’s the original case, but decades ago UK newspapers used to run competitions where they described a reporter and his whereabouts e.g. “Fred Smith will be walking along Bournemouth seafront today between 0900 and 1200 carrying a copy of our paper and wearing a red rose.”

If you challenged the right man: “You are Fred Smith and I claim my £5”, you won that prize money.

And here is the original ‘Lobby Lud’!

It is perhaps best known to the reading public from Graham Greene’s novel Brighton Rock where a similar device is used.

The original was Lobby Lud. (This would have been well known when Brighton Rock was first published)

Wonderful - ignorance deftly fought, thank you chaps!