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One famous face was absent at the State of the Union address to Congress last week – and it wasn't the designated cabinet member who always stays away from the Capitol building in Washington on these occasions, to provide continuity of government in case al-Qa'ida pulls off the big one. The missing person was Hillary Clinton, and the silly chatter predictably started.

Was it a deliberate snub? Had there been a falling out between Barack Obama and the woman he so narrowly defeated for the 2008 Democratic presidential nomination? Or had Hillary suddenly been taken ill? In fact, a glance at the diplomatic calendar would have instantly dispelled such notions. The US Secretary of State was away in London, attending important talks on Yemen and Afghanistan, a rather more productive...