Boston Consulting Group BCG London Insight Programmer interview questions

I was interviewed by an associate at BCG. The interview was 30 minutes, comprised of a CV section, a mini case study (with mental maths questions), and finally questions (from me). The interviewer was friendly though solemn. I was encouraged to take my time and given pointers during the case study exercise. The whole conversation was quite casual, and it didn't follow the strict structure because I asking questions about the interviewer's work very early on.