The first round of interviews was quite long. I went through problem scenarios with two Associates separately. The problems were not particularly difficult, although the second was more maths-focused. The Associates had answers and were pretty forgiving of any mistakes. They also asked questions about my experience and personal interests. After the two Associate interviews I had a short talk with a HR person - fairly standard interview questions. The experience was quite positive, all in all.
The invitation for a second interview came within a day. The interview also involved problem questions, but with two Partners. The scenarios were much less structured and quite difficult, and I found the interview questions to be much more rigorous in asking about my personal experiences. The first Partner who interviewed me was relatively new to the firm and quite pleasant. The second interviewer was a founding partner and I found him to be very impatient. He did not seem very interested in my responses and left the interview early when I asked for clarification about the problem scenario. It soured my experience and I was glad I was not offered a role.