I would like to make the journey Reading-Oxford-London-Reading. At Oxford I was told I can do this on an Oxford-London Travelcard: I just need to hold on to the ticket when I arrive at Oxford. At Reading I was told I can't do this: arriving at Oxford is the end of the ticket's validity.
The conditions say that my ticket is invalid (apart from further Zone 1-6 travel) after the completion of my return leg, but I would argue that this leg isn't complete upon my arrival at Oxford (I complete it on my return to Reading).
Which is the correct advice, and what are my chances of persuading the gate staff that my ticket is valid to leave Reading (where they will likely have seen me buy an Oxford travelcard) and on arrival at Oxford to keep it?