Got interviewed last year. The firm's pretty chat imo. First is a group interview, if you're lucky they'd be 3 other applicants and 10 if you're unlucky. They just want to know what you're like really. Nothing too mentally challenging but just pretend like you actually want to be an emotionless lawyer for the rest of your life and naiviely change the world. Anyway, best of luck.
Edit: Oh yeh, they will be making you to write an essay selected on a range of questions. Oh and a grammar exam.