Never mind the single/return thing. I once tried to travel from home to my uncle's house. He lives near a large city. This entailed:
1. train from Station A near my house into my home town.
2. train from Station B in my home town to Station C in his
3. him coming to pick me up in his car from the station.

Certainly sir, ticket to Station C will be £25. (Long time ago!)

Then it occurs to me that there's a station D where he lives - I could just get the train straight there, save him the bother of picking me up. Sure, it's another transfer, another twenty minutes and another ten miles further away, but hey, how much more can it cost? So I ask for a ticket to his home village...

Certainly sir... ticket to Station D, via B and C, that's £23 please.

EH?

So to go to C costs £25, but to go to D VIA C costs... LESS? What's to stop me buying a ticket to D, then getting off at C?

Nothing, I guess, sir.
(SonofRojBlake, Thu 23 Feb 2012, 18:42, 2 replies)

Those barriers you have to put your ticket in to get out of the station...
They won't let you out if you get off a stop early.
They don't in Truro anyway.
(Blahh, Fri 24 Feb 2012, 11:33, closed)

Then just ask the human to let you out.
It's perfectly legitimate to get off early (oo-er) on a walk-up ticket. It's not if you have an advance purchase ticket, in which case just buy the cheapest single from somewhere to Truro before setting off and use that to get out.
(ubergeekian, Fri 24 Feb 2012, 15:27, closed)

Legally
it's breach of contract.

www.thenorthernecho.co.uk/news/local/darlington/8415942.__155_/
( social hand grenade I was a lurker before you were a lurker, Fri 24 Feb 2012, 17:58, closed)

That Professor
had bought advanced tickets so not quite the same as turning up on the day??
(manwiddicombe is thinking of something witty to add here, Sat 25 Feb 2012, 15:39, closed)