Standard application, followed by a speed mental maths test, mostly simple arithmetic calculations the difficulty is the speed, practice basically. Also involved sequences. The next stage was a maths and coding test, testing knowledge stated in your application, e.g. data science statistics, and general maths problems as well as a few timed coding problems, e.g. on code acadamy. Following that there was an interview which involved discussing my background and a few maths problems. I was rehected following this.