I use this service a few times a year. When it leaves Glasgow at 10.12 reserved seats are sometimes not ticketed - a frequent occurrence - because the train arrives in at Glasgow late. I have sat in a seat and then at Perth someone boards and claims I am in their seat which they have reserved but wasn't ticketed at Glasgow. Am I obliged to vacate it? One time the ticket inspector found the person another seat but I didn't find out the "legal" position.