Is David Cameron prepared to attack Gordon Brown for being a Scottish MP? Now that the chancellor is all but certain to become prime minister next year, this is a salient question. For nearly a century, as the Conservative and Unionist party, the Tories have been committed to maintaining the United Kingdom. But in recent months, resentment about Scotland and the role of Scots MPs at Westminster has been building in Tory ranks.

The source of Tory angst is the constitutional settlement arising from the creation of a Scottish parliament nearly a decade ago. The Scottish parliament legislates on all matters affecting health, education and transport north of the border. But 59 MPs elected in Scotland continue to sit at Westminster, voting on these matters when they apply to England but not to their own constituents. Why, some Tories argue, should this continue?