I was on one of the first interviews and I think they've changed it since then, but we had an aptitude test to start, 20 questions, after that we went straight into a simulation where we had around 15 tasks to complete but not enough time to complete them. Roughly 4 hours, we had to self elect a project manager and they prioritised the day, if the project manager did badly they would be replaced... which happened... so I wouldn't suggest doing it unless you have good people skills and can think on your feet. Which I'd hope you could if you got through to the assessment day. We also had two 30 minute interviews with directors grilling you on why you wanted a career in IT and why you hadn't made the jump before, so come prepared. At the end of the day we had to present back what we'd done all day. 4 people were offered places on my assessment day out of 12. Three took the place with the other (the project manager) deciding that he wanted to go into project management.