Ah - but there's a 6 pound advanced fare on the evening train, via Swindon with a change there. So I don't think it's just the longer route that's kicked in advanced offerings. And on that evening train, it asks you what type of seat you want, then tells you that you're just being given an allocation as you can't reserve specific seats!
I would indeed have put this down to an "engineering weekend quirk" if I hadn't also come across the same thing - but less dramatic - in tickets for a journey I'm making on Friday of next week. Manchester Piccadilly to Church Stretton - direct train at 17:30. I can buy an advanced ticket at 25.00 ... or I can fork out a massive (
) 22.70 for an anytime day single, which saves me 2.30 and give me the flexibiity to drop back to the 18:30. What do I get for my extra 2.30 on an advanced ticket? Now I seem to recall a duty on ticket offices to offer the lowest available fare - does that mean that the 25 pounds advanced fare here is internet only, and if I go down to the ticket office they'll tell me to get the 22.70 single?