I was having my master studies at Bocconi University. I applied to a summer intern consultant position at Oliver Wyman Financial services. Since I am a Turkish citizen, I interacted mostly with the HR manager at Oliver Wyman Turkey office. First round consisted of 3 1-to-1 case interviews with 2 partners and 1 manager at OW- Milan office. After a week or so, I have been contacted with the same HR person from Istanbul office and she told me that I'll have a phone interview with the partner and head of OW Istanbul office. The phone interview consisted of CV and case interview. It lasted for about 45 minutes. After 15 minutes or so, the HR manger called me again and told me that the next and final round will be in OW London office. So after 2 weeks or so I went to London (travel expenses & accommodation paid by OW). I had 4 1-to-1 interviews: 1 with a consultant, 1 with a director, 1 with a senior partner and 1 with the CEO of Oliver Wyman Financial Services. Having the CEO interview was by chance I guess, not everyone has it. Overall the interviews were difficult but the consultants were friendly. And since the difficult was in math parts of the questions (which is my strong suit) I was lucky. In the end I got a very generous offer (2 days after the final round) for an intern and I accepted it.