In message
, at
15:03:53 on Thu, 24 May 2012, Sam Wilson remarked:
As I explain above, legal tender is irrelevant to this debate, as a
debt doesn't exist at the point of payment. There are other reasons
why this might not get to court, but that isn't one of them.

Though presumably a debt exists once the passenger travels on the train.
The debate then would be whether it should be treated as a simple debt
or an attempt to defraud punishable by a PF (which might be a fare or
might be a punitive fine levied under railway byelaws.)

If it was a debt then the traveller can pay using whatever legal tender
they have, but the ToC doesn't have to give change.

Otherwise a person waving a £50 note would never have to pay.
--
Roland Perry