I couldn't find the Oyster card points at Olympia last night (probably
because I was fuelled by 10 pints of Great British Ale) ... I honestly did
go back to take a look. Anyway, when I got to my destination I spoke to an
underground bloke who let me through with the words "You've saved yourself a
lot of money". So, my question is, how much is the fine for not scanning in
& out and only doing it on the way out. I guess maximum fare, but what is
that?

Thanks