Had three one-on-one interviews, each lasting around an hour. First was an HR interview, for telling you a bit about the company and to try and relax you. This was followed by two technical interviews. The first included a maths problem (which was fine for me given my mathematical background), and a discussion of previous projects I have worked on. The third interview was for me easily the toughest - I was asked to come up with creative solutions to somewhat vague technical problems. For example: - Come up with some ways to improve radiotherapy - There is some device in the eye and we need to non-invasively perform a mechanical change in it some time after it was put in. Come up with as many ways as you can to do this. I started by describing some areas in which I knew there was radiotherapy research. But he told me that he wanted me to come up with original ideas, not to recite what I've read about. Tricky! The process was professional, friendly and slick, they paid my travel expenses and the feedback was thorough and constructive.