Online tests, relatively standard and straight forward. Coding test was tougher for me as I have limited experience but still made it through this stage. Automatic video interview was very standard and competency based. The first in-office interview was half an hour with HR which started off competency based then had some quick-fire mental maths questions. Then an interview with 2 developers which is more coding based which I wasn't expecting and really struggled with. Finally got invited to a final round interview which was with 2 developers and a trader and looked into more depth of my knowledge of options pricing theory.
The interviews were interesting. My HR contact was really useful and kept me well informed and the process went through quickly. Annoyingly they don't reimburse travel expenses so they should really only do one on-site day and have both interviews then, it's a bit of a pain if you don't live in London. They also don't give any opportunity to see the office or meet people other than your interviewers whilst all other companies have been keen to show off their trading floor's atmosphere.
I ultimately declined the offer as I had another which was better suited to me.