In the supermarket, I went to a just-vacated self-checkout and found it was still saying 'Please take your change' and spewing out a five pound note and two pound coins. So I called "ooh, hey, excuse me!" to the woman who was leaving, not attracting her attention at all but making everyone else in the vicinity notice me. And a Sainsbury's worker grabbed her and returned the money, saying "It was that gentleman there!" in tones of awestruck admiration of my selflessness, and an old man said to me "It was really good of you to do that!" in the same kind of astonished wonder at having witnessed such a good deed.
Honestly, is that such an unexpected thing to see, even in these troubled economic times? I feel a bit of a fool for not thinking that I could keep the £7 myself until after I'd automatically tried to return it. I'll never make a master criminal.