They asked a series of standard interview questions, such as where I studied etc. and asked me to expand on the projects I had cited in my CV. They then progressed to give me a series of maths/physics/logic based questions to complete. The knowledge behind the questions were not too in depth but they really made me think about the way to approach the problem as they often would go against normal logic. It was to try and assess your thought process when approaching a problem, instead of just being able to do an engineering calculation.