In 2006, David Hesketh went from being one of the highest paid traders at Merrill Lynch getting offered "ridiculous" seven-figure salaries from fund managers, to living in a leaky tent in South Sudan, where he was confronted with a very different experience of risk than most traders ever have.

Sitting in his office on the edge of Shoreditch, Hesketh recalls swapping his trader job at Merrill Lynch for living in a "mud hut" where he worked in post-war reconstruction — and had guns shoved in his face. There were "AK47s wielded by 15-year old bodyguards, people threatening to kill me with machetes", he said. "Someone pointed a gun to my head and threatened to kill me in a market in Juba."