I can't find any reliable source for this claim. They range from "a friend who works in the Apple Store in Norwich"[1] to a "man who told it in the pub"[2] which makes me doubt its authenticity.
(Hence why I said "supposedly"; the claim, however, is trivially falsifiable, and I have yet to see anyone attempt to argue with it, despite I having been been posted around a bit last year. I realize that does not make it true, again hence "supposedly". Even if it was true at one point, it might no longer be.)
[1] http://blog.lewisking.net/post/318110435/apple-store-madness
[2] http://simonmorley.co.uk/2010/08/13/worlds-busiest-apple-sto...