Congratulations, that's amazing!
I would advise you try and think about "why Fieldfisher?" some more. Really research the firm, further than your application, and be prepped to explain why you like them so much. Also, think about generally why law and other motivational questions like that.
I would also think about your personal qualities, what skills you have and what skills you might want to develop or grow. Alongside that, prepare for general competency style questions. They cover a broad range of skills! There were 8 questions in total. It was supposed to last 30 minutes but I think mine ended up being closer to 45.
Good luck!
x
(there wasn't a great deal of emphasis on anything in the news, but I think current commercial awareness could be incorporated into other questions to really give your answers an edge. So it's definitely worth being aware of how businesses work, your sector interests and maybe the work the firm is doing in them?)