To the outsiders it would seem that things in Iraq got very serious very quickly. Did you see any of it coming?

“I’m very off balance on this. Most of us who watch Iraq have been surprised at the speed of this. I’m afraid so much attention has been on Syria and Ukraine lately that maybe we haven’t been concentrated enough. But a city like Mosul with 2 million people, that’s almost ten percent of the population of the country, I don’t think anybody honestly predicted that they would be able to take a city that size that quickly. “

Can you see a time when Britain or America would feel that they have to intervene?

“This is an absolute nightmare scenario . This group ISIS taking over parts of western Iraq is the worst-case scenario that any American planner came up with during the entire Iraq war. So the pressure on the US will really mount on this. It goes to the heart of everything they have talked about with the war on terror, all the anxiety about al-Qaeda and attacks on the homeland. I think yes, there will be a significant pressure on the US to do something.”

You call it a nightmare scenario. Presumably, part of that nightmare is the idea that Syria and Bashar al-Assad may now seem like a potential ally to the West, having been somewhat demonised.

“Exactly. In fact, you will see that with Bashar al-Assad. You may well see people arguing that we need to reach out more to Russia or Iran. You can see it already happening in the US. It is an enormous opportunity for states we have difficulties with in the past to present themselves as the voice of stability and encourage us to work with them to eliminate this Islamist group.”

Isn’t that going to be humiliating? You mentioned Russia and Syria there - for William Hague this is going to be the volte-face of all the volte-faces .

“We don’t see the Foreign Secretary saying he wants to do that but it is going to be very difficult for the international community as a whole. ISIS has been one of the most effective rebel groups against whatever we think about them. They control large areas of eastern Syria. If the West were to move against them, it would seem in the short-term that they would probably do is strengthen Bashar al-Assad’s government. Of course, he has been saying for two years that we need to work with him to tackle ISIS. So this is a very, very difficult foreign policy and defence choice for anybody.”

Doesn’t it though highlight a certain ham-fistedness on the part of Great Britain and the US in terms of how they have dealt with Middle East?

“The reality is that the US and Britain invested an enormous amount between 2006 and 2008 in a search in Iraq supposed to deal exactly with what we are facing now – the same Sunni insurgency. The fact that it popped back again four years later is a sign that ultimately their strategy failed and that the West with almost limitless resources at its disposal was unable to provide a lasting solution.”

Having lived and worked in Iraq, do you agree with the analysts saying that dismantling the Baathist army after the fall of Saddam Hussein was possibly a mistake?

“The invasion was the mistake. Yes, there are many other mistakes but in the end if you kept the army in place and haven’t de-Baathicised, even if you stopped the looting in Baghdad – we still would have been in enormous trouble. The basic problem was that the West didn’t have the knowledge, the power, the legitimacy to do this kind of operation in Iraq.

“The lesson we should take from it ultimately is a lesson of humility, not a sense that if we only did a few things differently, it all would have been fine.”

What is your feeling or understanding about the government in Baghdad to hold these ISIS forces at arm’s length. Do you feel that Baghdad is under threat?

“My instinct is that it will be very difficult for ISIS to get into Shia areas, or even the Shia areas around Baghdad. Nevertheless, they have surprised us again an again over the last few days. We have seen an incredibly well-financed launch. The Armed Iraqi army has essentially collapsed in the face of them. We have seen 40 battalions disappear out of the Iraqi army. So, I think making predictions at the moment is pretty dangerous.

“The Shia population is very large and very determined. I think it is unlikely they would allow Sunnis to dominate in Iraq.”