I have a mate who works there and he used to be a barber....so it cant be that difficult to get in!
On a serious note they will probably ask you why you want to trade, why you think you have what it takes, maybe some general questions about the markets like what is UK base rate, who is head of the fed, where did ftse close last night and all the other pointless stuff these places like to ask. They might chuck in some basic maths as well.
My advise is have a clear and concise answer in your mind of why you actually want to do this. Places like this prefer honesty and want to see hunger for the role. Have your own ideas about the markets with evidence to back them up and even if they are wrong at least you have shown the initiative and thought processes yourself.
Best of luck....
