It's currently illegal to have more than £1000 in cash on you without a plausible explanation and I think a police officer may confiscate it if you can't explain why you have it.

Banks are very excited about this. A year or two back I withdrew £8k in cash to pay for a vintage bike I intended to drive up to see and possibly collect on the spot. I changed my mind (surprise, surprise eh?!) and went to pay it back in the next day only to be met with a barrage of questions about where I got it from.

The cashier told me that if she wasn't satisfied with my answers she could refuse to accept my deposit. I think she may have been required to report it too but I'm not sure about that.

It all seemed a bit much but I suppose it also exposes the level of problems with money-laundering which, I understand, the UK might be a European leader in! I did explain that I'd got it from a bank quite like hers... These days I might be tempted to say I'd made it from doing a few haircuts, honest guv, innit!