Three stages, each with a different level of senior management. All of the interviews were based on 4-5 situation based questions, typically with something like "Tell me about a time when..." or "When did you last..." They are looking for Situation, your behaviors, and the outcome. How concise, coherent, and closely relevant the answers you give are all scored to give them a pass/fail rating. You get to do at least 2 of the 3 interviews regardless of how you fare. The final one only comes if you pass the first two.