The 17.57 from Euston to Lancaster on the West Coast Main Line on Thursday is £46.60. But if I book to get off at Preston on the same train - some 17 minutes and one stop earlier than Lancaster - I'm asked for £145. So, the same train, the same line, a shorter journey, yet triple the price. What's to stop me booking the Lancaster ticket and getting off early? Can I suggest to staff I'm breaking the journey up?