Why isn seat availability checked until the end of the booking process?
The website only checks seat availability at the end of the booking process, after you have entered payment details. This is because many people are using the journey planner at any time simply to check times and fares, and we do not want these to show on the system as seats taken. Showing “real time” information (i.e. how many seats are taken at that precise moment in time) at all stages of the booking process would mean a false number of available seats being shown.