Took place in their London office in the morning and lasted until the afternoon.
Involved an initial big group task with all other candidates where you'd be expected to work together on a leaderless abstract task. After that was a break where you'd have time to have water and talk with other candidates which was good after this you won't all be in the same room together until the end.
Technical interviews I recommend doing prior study into what it is hitachi rail do. They may not expect you to know exactly what it is they're doing in their day to day but in their questions you will get one or two which will spin you if you aren't clued up on it to some degree but overall if you don't know showing your process of reaching a solution can be enough to impress.
Behavioural interview, fairly straight-forward they would like to hear examples of how you've worked in a team, how you've met targets or expectations and how you've tackled difficult scenarios. Make sure scenarios answer the question.
Group task, was given a planning exercise to be completed in a pair theres a number of different exercises you're given they just seem to choose one and you and your pair work it out mine was to plan a journey between numerous different sites in a certain time period and only using public transport. For me this wasn't difficult however, looking back on my feedback i don't know if they just didn't like me very much or they mixed me up with another candidate becase it didn't seem to describe me or my contribution.