We had an aptitude test, a maths assessment and a set notation theory. We then had 3 short interviews with different interviewers (these were 1:1) where the questions were strength based as opposed to competency based questions. Each interview asked a warm up question and then a further 5/6 questions. It was fairly formal once you started the proper questions since the interviewers weren't allowed to prompt or help. They were able to repeat the question though and you had time to think before answering.