It's a prisoner's dilemma. You are caught indulging in insider trading along with your best friend. There are two choices: remain silent and hope neither of you goes to jail. Or confess to the authorities, get less jail time for yourself and throw your mate in jail. Which do you choose?

John Hartman chose the latter. And so it was that in the historic St James court building on a warm Wednesday in May, sitting only metres away, the 30-year-old former trader testified against former friend Oliver Curtis.