Phone interview first, then invited to the office for a full-day interview. First exercise was a paired programming exercise. A data-processing task using Python on a laptop alongside one of the interviewers, while the other interviewer looked on. Having not done one of these exercises before I struggled. If familiar with this type of interview, it would have been ok. If successful with this (which I wasn't) there would have been more interviews in the afternoon. The interviewers were really thorough and kind and chatted to me for an hour after the process, discussing careers and the company, which they didn't have to do!