Very quick process. Firstly, I had a brief phone interview with HR, very lightweight and informal. It was very much an 'About me' chat rather than questions and answers. Secondly I was invited to complete a Code Challenge which was pretty fun. Then came an invitation to meet with some senior members of the London team. The interview was split into two parts, one half was a chat with a senior strategist and the other half was a series of technical questions from two senior developers – questions were theory, code (on a laptop) and real life oriented. They told me I would hear from them in the next couple of working days and they didn't disappoint, I received my informal offer the next day and my formal offer 3 days after. One a side note, people were very friendly and offices looked really cool.