I did this process years ago, and it went very smoothly. Some chatting, some tests, and a presentation of your process for the case study. I really loved my time working there, which was for a little over 2 years.
The interview was divided into two stages.
The first one was with an HR rep, and the second was with the manager, both were very easygoing and pleasant to talk to
The process consisted for 2 rounds of interviews, one with HR and the other with your line manager. The first round was online and it was 30 mins. The second round was in person in their London office and also included a case study.