Recently, whilst trying to purchase a ticket for my sister on the fast-ticket machine at Hull (I had already purchased mine), there didn't seem to be any way of purchasing a child ticket without at the same time having to buy an adult ticket. How are unaccompanied children supposed to buy a ticket in the event of the booking office being closed? I'm guessing that on certain TOCs you could potentially be punished if you hadn't bought your ticket from the ticket machine and instead attempted to buy onboard.