Suppose I have a West Byfleet to Byfleet and New Haw ticket. If I want to travel beyond Byfleet and New Haw, say to Waterloo, normally I would have to go to the West Byfleet ticket office to get a ticket from Byfleet and New Haw to Waterloo. But what if the ticket office is closed? Am I allowed to buy the ticket on the train or do I have to get off at Byfleet and New Haw and buy the ticket from the machine there?