On Sat, 24 Jun 2006, asdf wrote:

Some have suggested that Chiltern should be allowed to charge a
premium to Met passengers. This perhaps could be achieved by the
Oyster system. If they were allowed to do that, perhaps other
national rail companies would be more in favour of Oyster
[...]
It would also be the end of interavailable ticketing, which wouldn't
be a good thing for the passenger.

Well, not entirely. Some other railway systems seem to manage to
define a base tariff (e.g for a season ticket), which can also be used
on premium trains by purchasing a one-off supplement per use.

I'm not sure how you'd tell an Oyster reader what your wishes were in
this regard, though.