Given the fact that there is at least one Paddington to Bristol Parkway service which is routed via Temple Meads it surely must be an acceptable route. Or does that logic only apply on the through service itself?
You can travel from Paddington to Bristol Parkway via Temple Meads so long as you do so via Bath. What you can't do is to use the return portion of a Bristol
Parkway to Paddington Super Off-Peak Return to travel Paddington - (Chipping Sodbury) - Parkway - TM. The ticket would have expired when the train arrived at Parkway.
Because the fare is the same, a pragmatic approach by GWR would involve not charging anything extra (and it's highly unlikely there'd be a ticket check during the couple of mins between Parkway & TM, or barriers in operation at TM in the small hours of the morning). But technically speaking you'd be committing an offence under the archaic
section 103 of the Railway Consolidation Clauses Act 1845:
103 Penalty on passengers practising frauds on the company.
If any person knowingly and wilfully refuse or neglect, on arriving at the point to which he has paid his fare, to quit such carriage, every such person shall for every such offence forfeit a sum not exceeding level 1 on the standard scale.
You would alternatively be liable to pay a Penalty Fare or for a new ticket from Parkway to TM.
It's not a theoretical discussion either; we've seen people penalised for travelling to Cardiff Queen Street on a ticket to Cardiff Central, even though the fares were the same. So it's a good idea to buy your ticket to the furthest station you might want to travel to, even if the price is the same.
Will correct my post actually, thanks - just tried and found valid itinerary for that route now you've mentioned it, had initially figured that the difference in distance between the stations was more than 3 miles and hence doubling back would be a problem, but I guess since they're within the same routing group it works out okay?
The Routeing Guide provision that allows doubling back within a Routeing Point Group (RPG) is only for interchange purposes, and only intermediately during a journey (i.e. not at a RPG that the origin or destination station belongs to). Thus this provision wouldn't cover the double back in this scenario.
It's also ambiguous whether the 3 mile rule would allow you to travel beyond your ticket's destination on a train that stops there - there could be an argument that s103 above would be engaged (in my view, this is different to doubling back where the ticket is specifically routed so as to include/require such a double-back, e.g. Watford-Manchester via London).
