First stage was a short written test after which you get invited back for a scenario based interview where you get told if you pass onto the next stage pretty much straight away. At both the stages everything was clearly described.

3 online screening tests, 1 in-person assessment centre, Role-play interview and a final standard interview. Must pass each stage to move on to the next. The online tests give results within a week, the assessment centre within 2 weeks, role-play interview on the same day. The whole process from application to final interview can take several months. Plenty of details online, especially in railway forums.