Submitted CV and cover letter online
Short 20 min phone interview, pretty standard, why are you interested in the role, a couple of problem solving questions like the SIM one which has already been detailed in other reviews.
Assessment day from 12pm-6pm with presentation and discussion with a senior staff member, 6 aptitude tests (logic, problem solving etc), and 5 min pre-prepared presentation from applicants on a controversial topic. Opportunity to talk with current trainees. Found it a bit strange that all tests were individual with no assessment of group work, but nevertheless an intense and enjoyable day.
Final 1:1 interview, around 30 mins, similar but a bit more in depth than the initial phone one, either in person or over skype depending on convenience. Standard interview questions, nothing designed to trip you up. All competency/personality based questions, no technical questions involved since you are trained by them for the first 4 months with the skills needed for the job thereafter.
Overall everyone very friendly and professional, very good with responding to questions throughout the process over email and on the day. I was told to expect a response before the end of the following week, but was notified of my progress either verbally at the end of the interview or by email the morning after each stage. Individual feedback was also offered at each stage.