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That North Korea has a uranium enrichment programme is not news; as long ago as 2002 the Bush administration told Pyongyang that it knew it was working along these lines. What is striking about Prof Siegfried Hecker’s revelations is how far the North Koreans have got in terms of installing centrifuges that can enrich uranium to weapons-grade standard. Along with a similar programme in Iran, these advances pose a daunting challenge to the nuclear strategy launched by Barack Obama in April and to the Non-Proliferation Treaty (NPT) that underpins it.