I hardly think asking the guard is bad advice. If the guard says "no" then that's that. If they say yes then that's that. There is no harm in asking!
You can debate the RG for the rest of eternity, but if you ask the TM if they will accept the ticket and they say "yes" then so be it - a victory for common sense! I'd be shocked if they say "no" but if they do, then just go to Euston.
I never said that they shouldn't ask the guard - did I? :-?. What I
was saying, however, is that based on the documentation in the public domain which apparently is sworn by, the intended route is officially invalid.
Now if a guard/TM says that they will honour the ticket then so be it - that is a different matter. What I say is that based on the routeing guide (alone), the WSMR is an invalid route. Sometimes, yes you get staff who follow every rule (some may call them jobsworths) so I wouldn't go to Marylebone and expect to get on if everything officially says no. If I do then that's nice but if not then I can't argue.
I can understand why it is thought this route should be valid, and indeed maybe it will be included in the next update of the RG, but it would appear that, at present, the WSMR is a valid route only for direct services - i.e. London - Wrexham, where as the routeing guide clearly says something like 'For direct trains, the route is valid for that train only'.
If he has asked the TM and he says yes, then that is that.
A chiltern barrier staff member cannot override a WSMR TM, in the same way that FCC or NXEC cannot override GC! However Chiltern are owned by the same company as WSMR so they are certainly not going to go hassling WSMR's customers and causing problems for WSMR, and a friend who works for Chiltern confirms that Chiltern staff are fully supportive of WSMR.
I'd like to see that in practice.
Passenger: 'This ticket won't work the barriers'
Barrier staff: 'Yes, because it isn't valid here - you have to go to Euston.'
Passenger: 'Can I just ask the TM if they'll accept it?'
Now at this point what happens? Do the barrier staff let them through if, in their opinion, the ticket is invalid? Or do they say no, and to go to Euston where the ticket is valid?
It's all very well saying that the barrier staff can't overrule the TM but how would you get to the TM first?