I applied via their website in April of 2013 for an internship position that summer. They got in contact within a 2-3 days via email and told me I had to take an online aptitude test. I received an email after that saying they'd filled all of their positions that summer, but to reapply September 1st. On September 1st I reapplied, but this time for a full placement year and not an internship. Since I'd "passed" the aptitude test a few months before, I didn't have to retake it. I was scheduled in for an interview at their Enfield offices. They paid for my travel and accommodation. At the interview I was in a room with two other candidates and we had to take another aptitude test, although this one seemed a bit harder. I didn't notice there was a clock in the room until after this test. If you're going in for an interview, make sure you use the clock to pace yourself. After that there were three long-form questions to go through. One was to devise a system for two philosophers in Greece to communicate using stone tablets and dumb slaves (tcp/ip analogy really). The next was to read five or so pages of assembly and say what the output would be. The last was to create some sort of algorithm to make a computer win more than it loses at a modified game of blackjack. Scores of 15 were worth 1 point, 16 2 points,..., 21 7 points. Red cards were negative, black cards were positive. After that I went in for a one-to-one interview where we basically just went over my application, which I don't think the interviewer read too well. He kept asking me things that were clearly on my application. Overall it was a fun process. I just flopped on a few questions so I didn't get an offer. If you practice ahead of time you'll nail this interview.