An entirely hypothetical situation you understand...
Went into the bank to transfer balance of savings account to new current account. Balance is £x00 higher than I expected. I query this and suggest there might be a mistake. Girl behind till checks a few things and seems to think all is OK. I mutter something about not being very good with sums, she laughs, transfers money, closes account, and I'm away scot-free.
Is there a time limit after which they can't claim money back? Given my (hypothetical, of course) history with the bank, I've no real qualms about keeping the money (plus there's always a chance I've actually got my sums wrong...). Just don't want to spend it and find a big hole in my account when they take it back.

