Online test followed by in-person day in Derby. During the day in Derby, they put our group of about 5 people together for an activity demonstrating teamwork / leadership. There were then individual interviews on general background and compatibility followed by a technical interview. I had a great first interview, but the interviewer for the technical interview was an arrogant guy from the Bristol office (Defence & Space). You could kind of say which areas you were more comfortable with, which I assumed meant engineering-wise, but I heard from another participant that she said she knew nothing about the Aerospace industry (or even that Rolls-Royce made airplane engines...) and so was given some basic maths questions. She was the only person to get the position by the way, which tells me they had a very particular goal in mind and honestly felt like a waste of time to fly all the way there. If you're looking at going for the grad program/internship, just say you are not comfortable with the harder topics and opt for something like calculus 1 as something you are comfortable with. Honestly though the vibe from the technical interview really made it a company I do not want to work for.