A ticket is valid unless there is some reason why it is not valid....
I see no reason to argue with that statement.
....So, I have an Anytime ticket routed Southern Only, the ticket has no time restrictions on the trains I can take, and it is valid on all trains operated by the Train Operating Company stated on the ticket - which, as the DfT confirms - includes trains branded Gatwick Express.
Therefore, on what grounds could the ticket be rejected?....
That only brings into question the use of trading names, as the Train Operating Company is Southern Railway Limited. "Southern" is only the trading name for a (major) part of the Train Operating Company.
In any case the NRCoC doesn't state train Operating Company, it says Train Company, which it defines as....
“Train Company” means a company operating passenger railway services which
is required to apply these Conditions to its tickets under a condition of the
Passenger Licence granted to it by the Office of Rail Regulation. A list of these
companies can be found in Appendix C. “Train Companies” means all or more
than one of these Companies;
And as both "Southern" and "Gatwick Express" are listed, both are 'Train Companies' as far as the NRCoC is concerned.
It is interesting you chose an Anytime ticket and not Off-Peak. Do you consider that an Off-Peak would need more wording on it?
....The same applies on Greater Anglia. If I have an Anytime ticket routed Greater Anglia Only (or whatever name they print on tickets these days; probably still NXEA Only for now!), it is valid on all trains valid by the Train Operating Company stated on the ticket, and that would include trains branded Stansted Express....
If Cross Country wanted to accept 'East Coast Only' tickets, what would stop them?
....Rather than claim that tickets can be rejected for no apparent reason, which is nonsense, you need to accept the fact that tickets are in fact valid unless a restriction (under Route or Validity) says they are not....
Like on Off-Peak tickets? or Rovers?
I don't deny that tickets are valid unless they are not.
....I think you need to stop considering the fact that Southern could use the Validity field to restrict some trains, because they have chosen not to, and even if they did that can only be done to the Off Peak category of tickets, not Anytime!....
Do they need to use the validity field to restrict some of their trains but not others? I haven't seen that written anywhere.
....Your logic is different to the logic of everyone else I've ever met.
A ticket is valid unless there is a restriction stating otherwise. It is not, as you seem to think, the other way round!
My logic is infallible in this case.
If condition 10 says that if the ticket is restricted to the
services of a particular company then it has to be printed on the ticket, then the
services have to be shown on the ticket to comply.
If condition 10 says that if the ticket is restricted to the services of
a particular company then it has to be printed on the ticket, then the
particular train company has to be shown on the ticket to comply.
So in your opinion, according to condition 10, what wording should appear on a Super Off-Peak Return, which is valid only for travel on the services of London & Birmingham Railway Limited, if it was not valid on any of the services provided by London & Birmingham Railway Limited that are timed to depart any station before 0930?