Applied online, was invited to do tests. Numerical test is super easy and requires only basic mathematical concepts - percentages, algebra, ratios. Financial Markets test requires some knowledge about different stock exchanges (HINT: CAC is located in France), Economics and accounting (know what appears on each financial statement).
Next stage was a video interview on FactSet's own platform. Mine lasted roughly 45 minutes, don't know if this is representative. Huge emphasis on the difference between IM and IB, as well what differentiates them from their main competitors (e.g. Bloomberg).
Was invited to AC in London afterward with around 11 other applicants. The morning consisted of a Microteach session and a group project. Microteach can be on any topic you want so make it interactive and engaging. Group project involves assigning priority to a list of tasks.
Lunch was provided around midday and then recruiters announced who had made it to the final interview stage.