I've found a fare where it is cheaper to go to a station further than I want to go to. Break of journey is permitted, so am I allowed to get the cheaper ticket even though I have no intention of travelling further?
A (made up) example of what I mean:
London to Cambridge Return: £12
London to Newmarket (via Cambridge) Return: £10
As long as break of journey is permitted (i.e. it's not an Advance, or one of the limited number of thus restricted Off-Peak tickets), you are perfectly entitled to make use of only part of the ticket's validity if you so desire.
You aren't making any representation to the train company that you actually intend to travel from A to B when you buy a ticket from A to B. All you are saying is that you would like the
right to be transported between A and B, and, if the fare is one which allows break of journey, that you would like the right to be transported between A, B and/or any intermediate station along the way.
By taking your money the train company then accepts that bargain of £££ for
[rights] - therefore the question of what you intend to do with the rights you are purchasing simply doesn't enter into it.
Hope that explains it a bit.