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CHANGE, indeed. On the campaign trail, David Cameron and Nick Clegg often sounded nebulous as they pledged a break from the past. They could not have envisaged keeping their promise in such concrete and spectacular fashion. As Conservative prime minister and Liberal Democrat deputy prime minister, they now run the first coalition government that peacetime Britain has seen since 1935.

Some kind of collaboration between previously antagonistic politicians was likely after the May 6th general election returned a hung parliament. Despite a fanciful attempt to cobble together a Labour-led coalition by Gordon Brown, who resigned as prime minister on May 11th, the Tories, as the largest party, were always going to be part of a new administration. But minority Conservative...