Great Western Coffee Shop

I'm curious as to why on 4th December

18:26 arriving 18:59
18:45 arriving 19:16

are both showing as valid for an off-peak ticket, but

18:33 arriving 19:02
18:33 arriving 19:31

are not. Is the window that narrowly defined ?

I think it may be defined by whether the train in question is an HST or not as well as by time.

Though that's an oversimplification

To some extent, I think it comes back to the old fashioned use of the word "peak" in that there are / have been certain second-level expresses and more minor station and line services where off-peak tickets have been acceptable even in what is otherwise a peak period.   I think some Cotswold line services, and services to / via Pewsey, don't quite fit the pattern ...

As a very rough rule, ex-Thames services aren't restricted, ex-GWT ones are. (But it's not quite that simple.)

Cotswold Line fares unfortunately do fit the pattern since the most recent validity changes - indeed, in some ways they're more restrictive than other tickets.

Nope. Previously replies seem to assuming travel from London Paddington. Perhaps the OP could have been clearer about direction of travel.

There are no evening peak restrictions from Reading toward London.

There's a long standing bug in online systems that erroneously shows a handful of trains from RDG to PAD as barred for Off Peak travel when they aren't. Something that has been discussed on this forum on a few occasions.

FGW/GWR either can't be bothered or just can't fix this bug, which has been there for years.

Rest assured, Off Peak travel is permitted on these trains. It just isn't possible to select them online.

Apologies, my -> was perhaps a little obtuse :)

Thank you for the concise explanation, my SO will be relieved to know she can board any Paddington bound train around that time.

Oops - oh yes!