I applied through a staffing agency. The process took 2 weeks. I interviewed at G-Research (London, England) in Oct 2017
Interview
I had 2 on site interview sessions, the first one consisted of 4 technical interviews of an hour each.
Two days later I had the 2nd on site session, consisting of 5 more interviews. The 2nd session was a mixture of both technical and personal (attitude) testing. It's aim was basically to meet the director and everyone in my future team.
Interview questions [1]
Question 1
All the technical questions were difficult, but reasonable and interesting problems, requiring you to think thoroughly. For the coding interview you can prepare by solving challenges on leetcode, hackerrank or go through an algorithms course of your choice. I can't tell more as I signed an NDA.