I took part in an Assesment Centre in Derby. It was split into three parts: motivational interview, knowledge interview and a group task.
I was asked in advance to prepare a presentation on why Rolls Royce would be a good place for me. I was asked a couple of simple questions about my presentation and questions about my motivation to do a particular scheme.
The knowledge interview tested hard knowledge rather than logical reasoning. Some questions were irrelevant to the position I applied for.
The group excercise was paper planes design, which was again quite irrelevant to the role.