Long answer questions, then online tests (quite challenging), then video interview (I'll list the questions below), then assessment centre. They have loads of assessment centres on a rolling basis in different locations and also it is not the final stage of the process so keep that in mind. The day is split into morning and afternoon - anyone they're not bothered about gets told they can leave after lunch. In the morning, there was an introduction exercise where you spoke to the person next to you for 10 minutes then had to stand up and introduce them to the group (measures presentation skills, whether you're nice about the other person, and can you get important information out of people). Then the group (of 12) was split into 2. 6 of us did the group exercise (which was difficult but not impossible - really tests teamwork and interpersonal skills) while the other 6 did the online tests again (they make you do them again to check you didn't cheat). The group exercise was the hardest for me and in my feedback I was told I was "too direct" even though I thought I hadn't made enough contribution. I thought it was strange that in a group of 12 there were only 2 girls and both assessors were men, and also nearly everyone was white. They should at least pretend they care about diversity! Only 3/12 got to the afternoon, where I think they do a 1:1 interview and an analysis task. Then there's a final dinner where they decide if they want you or not. Seems a very long process and the assessment centre was really tiring given some people had driven for 2 hours to get there.