Kat wrote in message ...

Because you can't! (Unless they've changed the rules since last Friday)
As I've mentioned before, if you load pre-pay now (by accident) you can
either wait until January and use it, or get a refund via CSC

Unless they've changed the rules very recently... Anything that you
have loaded onto prepay can be used to buy tickets at the big ticket
machines. The ticket won't be loaded onto the card, you will get a
normal, printed card ticket, but the money will be deducted from the
prepay balance. And as I discovered a few weeks ago, prepay seems to
work quite happily on buses equipped with Oyster readers. It only
charges you a penny for each ride mind you...

--
-sandy