Ask yourself why you are interested in the programme. Is that because you think you'd like to work at a firm such as Slaughter and May? If so, why? What do you think such firms do? Is it the pay package that attracts you? Is it the opportunity to work from morning until until past midnight five, six, or even seven days a week? I am not joking about the last bit, by the way.
You might wish to look at Roy Goode's book on Commercial Law, and perhaps at some introductory books about what goes on in those tall buildings in the City and at Canary Wharf. The Economist and the FT publish some guides. Maybe watch The Big Short.