We can't just leave this to the Iraqis to solve. It's disappointing that we know so little. We only know about where we look, and for some reason we weren't looking here. We probably don't need to do anything really quickly, but we've got to be very robust. Al-Baghdadi's ambition is not to just set up a caliphate that attacks the Middle East but attacks us too. We don't need to invade, but we can't let it slide either. This needs constant, relentless pressure to produce a sustainable political outcome, but that pressure may need to last for years.
The answer certainly isn't conventional forces. More likely is counter-terrorist advisory services, which will involve discreet elements of our armoury and that of the US. You're not going to solve this in a couple of months with drone strikes. We crippled al-Qa'ida in Iraq from 2005-10 but it took time. It required a sustained effort, but equally we're not going to have another Basra with dead British soldiers. The French didn't have that in Mali, and we didn't in Libya. Let's not let the military lobby lead the debate. Let the Foreign Office and the rest work out what we need. Whatever we do, don't deploy people from Horse Guards Parade to go and be targets in Iraq. It doesn't work.
Richard Williams is a former SAS commander