This happened to me last night and I was wondering if anyone
else had come across it. I was topping up my Oyster pre-pay
card at the touch-screen ticket machine at North Greenwich,
using up all the small change in my wallet. After about £7,
the machine closed the coin slot, and threw all my coins back
into the rejected coins/change tray. It sounded like I'd won
the jackpot at Las Vegas!

The message on the screen said "You have used too many coins"
(or something very similar to that).

So, I started again, but about half way through, pressed the
"Finished" button, updated my card, and then added the rest
of my coins in a second batch.

I am at a loss to explain why "too many coins" is a reason to
terminate the transaction. Surely they should be pleased that
I'm stocking up the machine's supply of small change? I wasn't
causing a delay since I had deliberately waited till my last
journey of the day before doing this. The coin box wasn't full,
because it let me add all my coins when I tried it in 2 separate
batches.

Not a major grumble, but a bit of a "head scratcher" - why was
this feature designed into the system in the first place?

Graham