The interview was made of two parts, the first being 2 hours and the second (which you attend if you pass the first stage) being 1 and a half. The first part is almost entirely task-based, at first being numerical questions (the kind you get asked in an timed numerical reasoning tests before the interview stages) and then a few case studies. The case studies are usually pseudo code questions (at least in my case) where you are given some example functions (such as a sub string function which returns part of a string variable given some parameters. They do suggest you look into SQL and XML prior to the interview as they could ask questions based on it, though you are more than capable of answering the questions without any knowledge in these.