I co-ordinated the UN Panel of Experts charged with improving implementation of the Security Council sanctions for a year and am often asked how effective they are. Clearly they have not halted the North Korean nuclear programme but they have almost certainly slowed it down and, judging by the constant shrill complaints, they are certainly inflicting pain. Perhaps not least, the North Koreans regard them as a humiliation – they bitterly resent being treated as a pariah and crave respectability.
Moreover, interceptions of illicit shipments under the UN sanctions not only cause North Korea great financial loss but damage its reputation with its customers and suppliers. It seems North Korea is finding it much more difficult to sell arms than it did only a few years ago.
There have been suggestions that sanctions affect ordinary North Koreans, but the Panel, which is also charged with monitoring this, has reported several times that there is no strong evidence this is the case. The country's nuclear programme, on which the regime has spent huge amounts of money that could have been used to buy food, is much more damaging to ordinary people.
The key to the international community's reaction to North Korea's third test will be China. China accounts for the great bulk of North Korea's trade and almost all foreign investment, and it is Chinese aid that has kept the regime afloat.
China has been torn between a growing recognition that North Korea is a problem and a reluctance to do anything that might destabilise the regime and possibly cause floods of refugees across the border. It also calculates that North Korea is a useful buffer against the US.
In recent weeks there have been several articles in China's official and semi-official media about policy on North Korea arguing different points of view – there seems to be a policy debate under way in Beijing.
We do not yet know how this will end, but if China decides to revise its policy and implement even existing (let alone any new) UN sanctions, then North Korea's position would become very difficult.
John Everard was UK ambassador to North Korea from 2006-2008, and wrote 'Only Beautiful, Please', Walter Shorenstein Asia-Pacific Research Centre of Stanford University, £12.99