Anyone Come Across Fake Twenties ?

Quite a while ago I collected some money from the Post Office for a client. As I was putting it away I noticed the edges on two £20 notes didn't look right and on closer inspection it was clear to me they were fake.

Good fakes, with foil and holograms, but fakes none the less.

I (or rather the client) was lucky. I phoned the Post Office straight away and the cashier said she'd just found another fake note and to bring them back.

I've not come across any others since, so can't say how many there might be. But it was fun to find them. I'd have liked to keep one, but as it wasn't my money and I wasn't going to pay £20 of my own money for the pleasure of owning a fake ...