Cliff, are you saying I am an old forgetful person?
In my defence, can I tell you when I was a young teenager, or maybe 11ish, I found £3 in my local high street and walked some distance out of my way to hand it in to the police station. They were openly staggered that I had bothered to do this - I know £3 doesn't sound much and I would definitely keep it if I found such an amount now, but it was worth more in those days (30 years ago) and was worth more to me then than £100 is to me now probably. Anyway, I felt a bit of a green fool for handing it in - the police made me feel that way.
I must admit the presence of CCTV hadn't occurred to me - that might put me off - and I didn't know that the money would be automatically reclaimeed by the machine and credited to the withdrawer's account. Knowing that, I might just guard it and wait for it to be reclaimed. But if it was a question of I have it or the next person does, who has no more claim to it than me, then yes, I would take it. Why not?
Last year, walking on the beach, I found a sodden £20 note in the surf, no-one around. Now go on, tell me you wouldn't have picked that up. I did and we had a nice fish and chip supper on the beach, watching the sunset, very romantic, very special memory, and no I didn't choke on a fish bone!
I know the £100 in the cash machine isn't quite the same thing, but I just wnated to show you how the boundaries can be blurred. (And also let you know how the police regard honest people who hand in money found in the street.)