Applied online, which was basically just sending your CV. Within 5 days I was at their office in Birmingham for an assessment day (very quick turn around!). They seem to only be interested in intellect, they are not looking for leadership skills or personality. There were a couple paper tests, one was programming and one was logic puzzles (you ca either do then or can't). I was chosen for a final interview with two interviewers and was given a math problem to solve in front of them. Overall, this was probably the least fun assessment day I've ever done.