There were two discreet face to face interviews at their Soho offices in London. The first lasted around 30 minutes, in which three senior members of the programming division asked about my programming background (typical for programming jobs), scripting experience, and experiences in both creating one's own software and modifying existing libraries.
The second interview lasts around an hour, covers the same kind of questions, but includes a tour of the R&D department. I was given the opportunity to ask questions of current staff members on the projects they were working on and how those projects tend to progress.