There are 3 main stages; an online test, an HR phone interview, and an on-site technical interview, although there may be other requirements depending on the role. For the most part, all stages are straight-forward and both interviews are quite flexible. For the on-site case study, expect an intense line of questioning after the fact that could go for as long as two hours. Technically, it's not difficult, just make sure you're able to give explanations for what you did/would do if you had another go.

CV+Cover Letter, PI test, HR Telephone Interview, Final Technical Interview. From when I initially applied to the last interview was around 2months. HR interview call was general learning about you, assessing your commercial awareness & knowledge of the company as well as some technical questions around benchmarking. Technical interview was an Excel test (not too much data, already organised for you) but had an 1hr30 mins to find key trends and create them in PowerPoint. After this, presented findings to two interviewers who asked more questions about the task (what would you have looked at if you had more time?). They also asked a brain teaser question (classic consultancy ones).