'If you were gonna rob a bank, and you saw the vault door there, left open, what would you do? Would you wait around?Ever since he was a kid, kicking broken footballs on the streets of East London in the shadow of Canary Wharf's skyscrapers, Gary wanted something better. Something a whole lot bigger.

Then he won a competition run by a bank: 'The Trading Game'. The prize: a golden ticket to a new life, as the youngest trader in the whole city.

A place where you could make more money than you'd ever imagined. Where your colleagues are dysfunctional maths geniuses, overfed public schoolboys and borderline psychopaths, yet they start to feel like family. Where soon you're the bank's most profitable trader, dealing in nearly a trillion dollars.

A day. Where you dream of numbers in your sleep - and then stop sleeping at all.

But what happens when winning starts to feel like losing? When the easiest way to make money is to bet on millions becoming poorer and poorer - and, as the economy starts slipping off a precipice, your own sanity starts slipping with it? You want to stop, but you can't. Because nobody ever leaves.

Would you stick, or quit? Even if it meant risking everything?