There's an issue waiting to explode here. We had the millionaire's daughter a few weeks ago (if I remember rightly, she was entitled to a child fare but was refused) and now we have on the thread parallel to this someone who isn't entitled but who was buying child tickets.
At some point, the media will pick up on this in a big way, and there'll be a good old muddled moral panic with (probably the same) commentators arguing that fare evasion by adults buying child tickets must be clamped down on while for the safety of our children they must be allowed to get home even without a ticket. That'll be fun while it lasts.
As a first step, it really would help if the transport industry as a whole could come up with a common definition of when you move from buying child tickets to adult tickets. I'm not really too fussed as to what that age would be - it just needs to be uniform so on any bus, train or tram a passenger will have no reason not to know what ticket to ask for. Getting this in place should present no difficulty for anyone skilled in herding cats (which isn't much easier than herding transport undertakings).
Secondly, there are various schemes out there that provide proof of age cards. My impression is that most of those these days are to prove that you are old enough to do something - but I don't see any reason why the idea can't be flipped to have a card proving that you are young enough instead. If it comes to that, whoever issues railcards has the mechanism for producing photocards: how about a free / low cost 'child railcard', followed (subject to data protection) by an invitation to buy a young person's railcard when the top age is approaching?
Moving on, is there some way of guaranteeing that (alleged) children will get to their destination safely while protecting the railway's revenue? To just say that some sort of free ticket will be issued is asking for trouble. But (in cases of doubt - if someone is undoubtedly of age for a child ticket there's nothing to worry about) how about issuing a child ticket - but only on condition of the 'child' providing their name and address. The railway could then follow up with a notice requiring EITHER payment of the difference between the child and adult fare OR proof of entitlement to a child fare. This isn't a fool proof plan - it wouldn't deal too well with false names and addresses, and would potentially generate a lot of low value debts that would have to be expensively pursued to avoid the scheme coming into disrepute - but it would at least allow trouble free, fare paid travel for those young people who wanted to pay the right fare (but no more) and a clear deterrent (a letter to your parents asking for money) for those who are trying it on.
