I used a prepay card yesterday for two trips in Z1. The delay in being
recognised (compared to an Oyster) was very noticeable. It didn't appear
to me to be fast enough to allow an uninterrupted "walk through".

So far all that's shown up on the card is a 10p charge from TfL (probing
to see if the card is valid, perhaps).

TfL on the other hand are showing two lots of £2.30 in my online
account.

Didn't stay long enough in any tube station to activate my Virgin Wifi
though, but did at least get as far as the sign-on screen this time.
--
Roland Perry