The extent to which politics has changed in the wake of the Paris attacks can be seen in the confidence with which the prime minister is now talking about a “comprehensive strategy” to win MPs’ support for air strikes against IS in Syria. Given the reservations expressed about the idea recently by the Foreign Affairs Select Committee, not to mention the consistent opposition of Jeremy Corbyn, the Labour leader, this shows how fast we have moved on.

And that includes the Parliamentary Labour Party. Before the attacks many Labour MPs would have felt obliged at least to abstain from a vote on air strikes — which Mr. Corbyn opposes in the absence of UN authorisation — though a solid group of backbenchers would always have voted in favour of them on principle. But now, given the devastating criticism of Mr. Corbyn’s stance on security this week by the PLP, it seems far more likely that Labour MPs will feel able to support the strikes. Mr. Corbyn can hardly appeal to party discipline, given his own record.

More importantly the public mood is changing. As we report today, polls show a fairly even split on backing air strikes in Syria — unsurprising given the wave of popular sympathy for Paris. Indeed, France has invoked the little-known clause in the EU treaty that allows any member state to call on the others to aid with military assistance.

It was very different when Parliament voted against air strikes in 2013. That vote was a valid expression of unease about a flawed policy which had identified the admittedly repellent Assad regime as the main problem in Syria and his removal as our main objective. This was a problematic approach even at the time. The unpalatable truth is that President Assad was and is the lesser evil in this conflict and IS should be our real target, given its record of genocide against the Yazidis, mass rape, the annihilation of minorities and the destabilisation of the entire region. It is inconsistent, as Mr. Cameron points out, that we should bomb its forces in Iraq but not in Syria, given that its centre of operations is Raqqa in Syria.

But air strikes can only be part of a larger endeavour to bring an end to the war in Syria. That would mean a deal to include all the main players, not least Russia and Iran, President Assad’s main supporters. A deal that accepts that he may remain in power for now in return for stepping down later is within reach. Now is the time to act; we cannot leave the fight against IS to others.

— The London Evening Standard, Nov. 18