One video call, followed by a face-to-face interview, then a third group interview. for the second interview they require 2 take-home assignments, one of them being statistical analysis, and the second being a program planning presentation/ task. Their interviews tend to be very lengthy with my second interview with the founder, Simon, lasting more than 3 hours. The interview process is VERY effortful and time consuming for a couple weeks.
After the third interview, they offered me the job and we discussed salary, I made my case for a higher pay than they offered as one should. They said they needed to consider this request. They took 2 months after this to reply substantially despite several messages politely requesting an update.
Eventually the founder offered me the job at the original offer, and requested I start work in November, I accepted. I made preparations for this, but they did not send me the contract although they said they would. After chasing, he called me and said he was uncomfortable hiring me since I had attempted to negotiate a higher salary (whut?), he also said they decided they didn't want to higher for the position anymore (the ads are still up).
TLDR: Probably a good idea not waste your time with these fellas.