I applied online for the HK office from university in the UK, received an invitation to the first interview after about 1.5 months after submitting my online application. They normally interview in the regional office where you are located so I was interviewed at 55 Baker Street, London. There were 2x 30 min interviews, first one included general personality questions, why i'm fit for the role, and a guesstimate question (which they call case study as well), second interview was basically CV grilling and competency based questions, questions were about leadership styles, what motivates you, my interests stated on my CV. They were just standard questions about your experiences so prepare them with the STAR method.