3 rounds. First interview was with an associate, comprising general questions and the classic "how many passengers pass through changi airport annually" question. Second interview was by far the most taxing: 2 case studies with 2 separate senior managers; one was a real case currently underway at Accenture, the other was a general issue about poverty. Entire event took about 3.5hours. Final round was with a managing director - just general chit-chat and informal questions probably to find out if you fit well with the team.
Entire process took about 3 weeks from first invitation to offer.