Cameron will need Miliband's support to win a vote on military action. But all the signs are that he will get it.
The Islamic State video appears to show the killing of a third Western hostage, aid worker David Haines, and ends with the warning that another British person will be next.
Iraq, Libya, Syria, Nigeria, Afghanistan are all in danger of becoming black holes in which the nastiest groups can thrive. The only credible solution is to turn them back into proper countries.
David Cameron hinted that the UK will soon join the US in air strikes on Islamic State.
From Riyadh via London to Damascus, Baghdad and Isis – the jihadist surge.
There are severe limits to what the UK can do as a middle-ranking power. But it can do better than firefighting every crisis with an emergency meeting of Cobra.
The most crucial of all decisions – to go to war – must not be left in the constitutional and procedural shadowy shambles it currently is.
The PM is not alone in failing to articulate a clear set of principles for this new era.
Making a global spectacle of the murder of a western journalist carries a uniquely powerful propaganda message for the jihadists.
The people’s representatives should be able to exercise their democratic role, whether it is convenient for the prime minister or not.