May have changed since year before last but:
1. Partner Interview:
i) Was definitely asked Why Law, Why Commercial Law, Recent deal. Then there were competency questions.
2. Case Study:
i) Think out loud if you are trying to find the answer, they're not trying to trip you up but see how you get there too.
3. Written Exercise:
i) Make this look pretty - headings, paragraphs: short 2 line intro, rule of three (firstly, secondly, lastly), and conclude 2 lines (overall, I would..) is a good rule, I think they let you make tables, make sure you finish.