I got on the bus because i didn't hear the 'reject' sound, it's an easy mistake to make. There was a scrum of people crowding onto the bus, you have a split second to swipe your card before the person behind you swipes theirs (it wasn't a 'bendy-bus') However i wasn't aware of the top-up scheme, so many thanks for pointing that out. I've had to get off the bus on more than one occaision because there were insufficient funds on the card, only to have to walk half a mile to the nearest newsagents to top it up. Perhaps if TFL spent as much money publicising the top-up schemes available to pay-as-you-go users as they do threatening people with legal action, the problem would be reduced. However i'm still curious to know why the Revenue Inspector did not follow procedure.