Well, sort of. It's about tickets rather than locomotives, but you have to be a bit of nerd these days just to avoid paying a zillion pounds to go anywhere.
Anyway, just suppose I have bought an Advance ticket, and it is for the 20:08 from Bristol Parkway to Swansea. I am waiting on the platform at Bristol, and the 19:42 to Swansea is delayed, and is now expected at 20:13. The 20:08 to Swansea is delayed by an uncertain and growing number of minutes - latest prediction is 20:32. Now, obviously I'm going to get on the train that departs at 20:13, because a) it's the obvious thing to do and b) I'm scared of missing last orders at the pub thanks to an indefinitely delayed train. But is it allowed, or is it against the rools, given that the "20:08" on my reservation arguably refers not to an actual time of departure but to a specified service? Do the rools require me to wait for the next train? Has anyone ever tested this and had a barney with a ticket inspector as a result?
Yours interestedly
TeeCee