Was a very relaxed and professional environment from the start. I was quite early to the venue, and was sat in the waiting area talking with some other candidates. I would recommend doing this, as you also will get a chance to relax a bit and get to know your peers. The assessment center began with a short introduction of the company and the interviewers, followed by a plan for the day. In my case, it was a technical presentation, followed by a 1-1 interview, followed by a group exercise. My advice in general, would be to learn as much as possible about the company and really figure out why you would want to be there... Relax and be yourself, at the end of the day they want to see if you can work well with them, not if you can remember every last equation from university...