I had to complete a test, consisiting of a few math questions. They provide a very good outline of their expectations for you in a file they send you. The test and the first interview are largely consistent with their interview guide. After one interview, I was surprisingly called in to London for a final round. It was a whole day interview, where I had 3 separate interviews with different teams. The next day, the lead of the team that liked me best had another interview with me. It was an NLP specific role, so I got asked about recent NLP methods and my experience with them.