As the countries of the United Nations wrangle over the sanctions to be imposed on North Korea following its nuclear test this week, doubts are being cast on the effectiveness of whatever measures are agreed.

With China and South Korea fearing the collapse of their volatile neighbour, and with a large proportion of North Korea’s income coming from illegal trade, even targeted sanctions would have a limited impact. The regime has already survived the death of its founder and a famine that killed up to 10 per cent of its population.