This is TicketySplit Lite, which is designed for use on mobiles. If you're on a desktop, please use the improved full TicketySplit tool instead.
This tool doesn't cover return fares yet. If travelling there and back, return tickets often beat singles, so always get a quote for these too.
Beware split-ticketing at stations where you change trains. If your service is delayed and you've a time-specific ticket, you may need to pay extra. Non-advance fares listed in this tool shouldn't specify a certain train. But if you purchased an off-peak ticket that requires you to travel at specific times of day, and the delay takes you outside those times, you'll have to pay again.
The train MUST call at all the stations you buy tickets to and from. This tool only splits tickets at stations where trains stop, but watch out if you're finding splits for yourself on booking sites.
Walk-up fares include anytime, off-peak and super off-peak fares. Off-peak & super off-peak may require you to travel at specific times of day, days of the week or on a specific route. Double-check the ticket's conditions at the station.