I first had a technical interview with a recruiter from IG, where they did not ask me any technical questions at all but rather they just asked me about why I wanted to work for IG. They then offered to put me through to an assessment day. The assessment day consisted of a technical java test, a pair programming exercise with one of their developers, lunch, a group activity and finally an interview. On the day, some candidates had their schedules in a slightly different order but everyone did the same thing by the end of the day.
The technical test was ok, just a few question on java syntax and some threading questions. The second section of the test was a list of acronyms and keywords, where we had to describe what each meant/what it did. This was a little more tricky as some keywords were quite obscure.
The group activity was a simple design and pitch task where groups had to come up with a product and pitch it to "buyers". Then finally the interview was held with a technical lead from the company as well as a graduate manager.