Let me try again. I was not asking about jurisdiction in general.
Can you point to a case where Magistrates or a higher Court have thrown out an 18.1 prosecution on the grounds that the offence was committed in Scotland but detected in England?
Or indeed a case where the defence was successful that the offence under 18.1 is only committed at the moment of boarding, and therefore the fact that half an hour later the defendant had no valid ticket is irrelevant?
There is no case law on your specific questions, as far as I'm aware, because properly defended Byelaw prosecutions are by the very nature of the offence, and its level of seriousness, rare. Not to mention the fact that, being conducted almost invariably as private prosecutions, the TOCs often become shrinking violets as soon as they realise they've picked a fight with the 'wrong person' so to speak, and drop the case.
But nevertheless - in the case of the first question it appears you're asking for me to show case law that simply backs up the matter of jurisdiction, which I have already answered in depth in the previous response. What is relevant is where the criminality takes place - its discovery is a subsidiary consideration.
And in the case of the second question it appears that you're asking me to show you case law that shows that a Byelaw 18(1) offence is committed when the circumstances given by 18(1) are met. I'm not sure how you expect me to explain that any further. 18(1) is perfectly clear (unlike RoRA) and can't be interpreted any other way - "no person shall
enter any train...".
If the TOC wishes to prosecute an illegitimately ticketless passenger they could, accordingly, do so under Byelaw 18(1) or under 18(2). Which specific charge they go for will probably depend on their evidence - if the defendant claims to have lost his ticket on the train, then it would be easier to go with a Byelaw 18(2) prosecution. If he doesn't allege that and instead produces a ticket, but one that isn't valid, then a charge under 18(1) would be easier. But they are two clearly separately defined offences and so I don't see what bearing the second part of your question has on 18(1), or indeed what relevance your question has to the OP's situation.