I am not convinced that the new trains being shorter* gives an automatic entitlement to use first class with a standard class ticket. Nor does the failure of GWR▸ to honour reservations give such an entitlement
Current Conndtions of Travel:
Unless you have made a reservation please note that your Ticket does not automatically entitle you to a seat, and at busy times you may have to stand. You will not be entitled to any refund in these cases unless you hold a first class Ticket and no first class seats were available on a train service where the timetable indicated that first class seats would be provided. More information on the refund to which you are entitled in such circumstances can be found in section 31 of these Conditions.
and
Unless Train Company staff, or notices on the train give you specific permission, you cannot travel in first class accommodation (including standing in corridors or passageways) with a standard class Ticket. This applies even if there are no vacant seats in standard class.
Conditions of Carriage to 2016Travelling in first class accommodation with a standard class ticket. If you have a standard class ticket (other than a Season Ticket), no standard class accommodation is available, and staff on that train give their permission, then you may travel in first class accommodation (or the equivalent) where this is available without extra charge.
Current conditions seem to make it very clear that you cannot travel in First class on a standard class ticket unless given permission by train company staff. I might agree that's pretty harsh if you've reserved a seat, but the carriage it's in isn't available and there are no other standard class seats available on the train, but I think the correct action in such a case may be to either reclaim to ask a member of the
TOC▸ staff.
Part of me asks "why should a barrister be able to bluster his way through a circumstance that the rest of us would just give up on and pay up", but then the other part of me thinks "thank goodness someone stands up for his rights" (even though it sounds like he wan't in his rights!!).
As described, the ticket examiner clearly made his pragmatic decision not to take the matter further at some point between moving on and the train arriving into London - he's perfectly entitled to do so. His error was in dropping (in error, I would suspect) the barrister's business card.