One of the more significant constitutional innovations of recent times is the assumption that the government must get parliament’s permission before committing British forces to military action. This precedent, set with the 2003 Iraq vote, has been upheld by this government; it famously resulted in Britain not bombing Syria in 2013 following the use of chemical weapons in the civil war.

There had been pressure on the government to formalise this new constitutional convention, to legislate that the government needs parliament’s permission before military action can be taken. But in a written ministerial statement today, the Defence Secretary Michael Fallon rejects that option. He makes clear that while the government will continue to consult parliament before action is taken, it wishes to reserve the freedom to act without prior approval in extraordinary circumstances. This strikes me as sensible. There are occasions on which the pre-emptive use of force would be justified; and that is, obviously, not compatible with a parliamentary vote.