The last sanctions report said Japan had declared that 34 pianos, four Mercedes Benz limousines and cosmetics had been exported to the North by Japanese trading companies now awaiting punishment.

But there are holes in the sanctions regime.

Japan discovered that North Korea was exporting food items such as mushrooms to China which were then sold to Japan at higher prices, according to Leon Sigal, head of a North Asia security programme at the Social Science Research Council, a New York think tank…