I applied through a recruitment agency and the entire process took about 2 weeks. I've been asked to fly to London (no expense refund) to have the interview.
First of all, I've been asked to leave all my belongings in a locker and then I signed an NDA, so I'm afraid I cannot disclose the questions I've been asked.
I had a technical test and after that, since I passed, three face to face interviews with three different members of the team: a junior, a recently promoted senior and the manager of the team.
I heard about the results two days after the interview: my technical skills were a good match, however the manager doesn't think I'm a good fit for the team.
Overall it was a pleasant experience, everybody is very kind. I'd recommend applying for a role at G Research: very interesting company and great location