It still wouldn’t necessarily constitute intent to avoid payment if the TOC can’t reasonably disprove the story that he had a ticket in the first place (it’s a bit like a no money/no ticket not automatically being proof of intent to avoid payment, contrary to a what a lot of revenue staff believe). This passenger was cooperating to an extent, so the TM could quite easily have taken a harder line with him in the first place to at least test the water.I guess if you just chuck them off at the next station they disappear, but if you ring ahead BTP may be able to meet the train later in its journey and the person may end up being brought to book for whatever they are carrying. I imagine also if you tell them to leave the train at X and they are still on board at later station Y, that would constitute intent to avoid payment.
I also don’t like it when on board staff take the approach of “get off at the next station, go and see the barrier staff and it’ll be fine, just get the next train” or words to that effect. It’s passing the buck and potentially causing problems for other staff when they do their job properly and don’t left him travel any further.