Very old fashioned refund...

Last week I ordered a second hand book online. A couple of days later I got a message from the seller saying that he hadn't been able to find the hardback copy that I'd ordered, and would I accept a paperback version and a ten pound refund. I agreed very happily - I actually prefer paperbacks and hadn't noticed that it was available. A couple of days later I received an envelope in the post with a printed receipt and a ten pound note! This was not how I expected to get my refund.

The book hasn't actually arrived yet...