It is September 2012 and I am at the National Security Council in Downing Street. David Cameron is chairing a discussion about military options in Syria. Almost 40,000 civilians have been killed and thousands are displaced. The Chief of the Defence Staff explains how to establish a no-fly zone on Syrian territory and create a safe haven for refugees. Next up the heads of the intelligence services assess the opposition groups, some of whom are Islamist extremists. After a lengthy exchange of views the ministers agree not to take military action.

Fast-forward to August 2013, President Assad has used chemical weapons against his own people. Western powers are threatening military action. In a bizarre twist, I am in Afghanistan before the crucial vote in Parliament, with my inbox full of draft speeches about Syrian intervention: a tough juxtaposition as I visit the last forward operating base held by British troops in Helmand, the tail end of a 12-year intervention. Back in London there is high drama, the Government loses the vote on Syria and President Barrack Obama rows back from his commitment to bomb Assad.