My thanks to the reader who mailed me with the tale of the note he had from the Post Office who had tried to deliver a letter while he was out. He works from home, so assuming it to be an important work letter he went to the Post Office where they had a stiff-backed letter with insufficient postage on it. He paid the 20p plus an extra £1 for admin costs.
It was a piece of junk mail from NatWest asking whether he'd like a business credit card.
He's considering invoicing them for the amount he paid, plus time spent chasing their underfunded piece of junk , then there's the call-out charge...