The written test (math / finance / excel) was a breeze. Following that, I had a whirlwind process where I interviewed with 5+ senior staff; also had to do a brief presentation. As I had prior experience, most of the questions were centred around my motivations and why I wanted to work at the firm. One can expect a lot of behavioural / fit-based questions and can be thrown unrealistic / bizarre hypothetical situations. You have to be convincing enough for them to reckon that you aren't a flight risk! Expect stuff around your inclination to hop across to the client side and don't sound ambitious.