Almost 80 per cent of ConservativeHome’s Party member readers support bombing ISIS in Syria, according to last month’s survey.  One Conservative MP who agrees with this majority is one of the most senior: Michael Fallon, the Defence Secretary – who has said that taking the fight to ISIS in Iraq but not Syria is “illogical”.  Quite so: the Sykes-Picot borders no longer exist, and Syria’s likely fate is to be carved up into sectarian zones – a tragedy for a country which until recently combined clan tyranny with religious tolerance.

The Americans and other members of the coalition combating ISIS want British support for cross-border bombings – not least because our Tornados have the capability to carry out precision attacks.  But both Fallon and David Cameron know that they need the support of more than 80 per cent of other Tory MPs if such action is to happen.  Memories of the Government’s humiliation over proposed strikes against Assad two summers ago still haunt Downing Street.

As we argued at the time, it made no strategic sense to assail him; there was no “Plan B” in place were his regime to continue chemical weapon attacks, and it would have been foolish to win a vote on these strikes in the face of Conservative backbench opposition and off the back of Labour frontbench support.  What scuppered Number 10’s plan was that the latter was not forthcoming.  Ed Miliband first offered support to Cameron and then withdrew it…all in the space of a single afternoon.

Although there is no legal requirement for a vote now – any more than there was in 2013 – extending the bombing of ISIS to Syria is politically impossible without one.  Feelers have been been put out to Labour’s interim leadership: Harriet Harman, Vernon Coaker and Dan Jarvis have been briefed at a meeting of the National Security Council.  But Harman will be gone by the end of next month, and Coaker and Jarvis may both have been reshuffled or sacked…or refuse to serve.

The latter prospect will arise if Jeremy Corbyn wins: Coaker has already indicated that he won’t take a place on a Corbyn front bench.  The Government may be able to peel enough Labour MPs off such a leadership to carry a Commons vote after we get a result, but the gambit would be dicey.  According to Government sources, Labour’s interim leadership has three main concerns about extending the bombing: first, that nothing must done that will help Assad; second, that any strikes are legal.

This preoccupation is a legacy of the Blair-era invasion of Iraq.  The third reason is the age-old question: “What happens next?” – in other words, what’s the plan if bombing in Syria has no effect on ISIS’s capabilities.  But there is no reason why strikes against ISIS’s command-and-control centres in Syria, or against strategic targets, should lead to British boots on the ground either there or in Iraq.  This being so, they should happen.  However, a legacy of the Corbyn surge, whoever wins Labour’s contest, is that getting its support for bombing in the autumn will be as problematic as ever – if not more so.