Chris wrote:

In other words the Oyster is still charged for a journey when it is
rejected as not valid! Something wrong here.



RTFM
1. The Oystercard recorded you entering the tube system.

2. You didn't exit the tube system by the card openning a gate for you or
by being let out by a memeber of staff and having your card correct by sed
member of staff.

3. So the Oystercard has no record of the station you left at

4. Hence it charges the maximum fare possible

Actually, does it do this? Recently I made a journey from Hammersmith to
Norbiton, touching in with my PrePay at Hammersmith Tube, changing from
tube to rail at Richmond, forgetting to touch the transfer out because I
could see the connecting train was just arriving and belted over the
bridge. (Also meaning I didn't get a rail ticket, but I digress).
Obviously at Norbiton there are no Oyster touch pads.

From memory the Oyster card went down by about a pound - which I
thought strange as I was expecting it to drop by the maximum charge. But
when I next recharged it there was a message on the screen saying that
there was an unended journey, and would I visit a ticket office to
resolve the issue? (Which I must admit I have yet to do ...)