The crisis in the Gulf provoked by Islamic State could last for 10 to 15 years, says Sir John Jenkins, Britain's former ambassador to Saudi Arabia.
Sir John, who left the Foreign Office last week, said it was probably the worst crisis in the area since WWII.
Over his 35-year career Sir John served in Iraq, Syria, Libya and Israel.
He said countries in the Gulf were facing unique challenges and were unsure about the support they were getting from the West.
"Speaking quite frankly, people do wonder about the level of commitment that the western alliance and particular countries are prepared to make to the security of the Gulf in this age of anxiety," he said.
In an exclusive interview with BBC Newsnight, Sir John said he would not defend Saudi Arabia from those who have criticised it over the lack of progress to further women's rights, and the flogging of the blogger, Raif Badawi.
But he suggested there was widespread ignorance about what was really going on in the country - and people needed to go there before coming to judgment.
During his career, Sir John was regarded as the Foreign Office's foremost Arabist.
"This is probably the most challenging set of circumstances (for) countries in the region, particularly in the Gulf, since the 1960s and maybe since the end of WWII," he said.
"There's a whole set of physical and material challenges to the national security of these states, but (it's) also ideological."
He added: "I wouldn't be surprised if we were looking at 10-15 years of instability and insecurity in Iraq and Syria and in parts of north Africa."
Sir John said anxiety about how to deal with IS was compounded by uncertainty about the West's commitment to protect the region.
"There was a time when you could simply say the answer to everything was to increase the strength of a naval flotilla, for example, in the Gulf or naval task forces off the Horn of Africa.
"I think it is far more complex than that now and I think we are all trying to work out how we deal with that."
He said it was "astonishingly difficult" to find common ground between countries over how to deal with Syria and admitted the international alliance set up to tackle IS - or Daesh as it is called in Arabic - "was not particularly cohesive".
Sir John said a key to defeating IS was mobilising Iraq's Sunni population against it.
"You have to have a way of mobilising the population as a whole against Daesh. Do I think that Daesh represents a majority of Iraqi Sunnis? No, I don't.
"But I think they represent a fairly significant minority and I think there is an alliance of convenience between people who are genuinely committed to this absurd extremist narrative (and) former Baathists, army officers and so forth who are fighting with them...because they feel this is the way of getting back at the Shia.
"But the only way to deal with this is to persuade a sufficient number of Iraqi Sunnis that it is in their long-term interests to support an effective, accountable, and benign Iraqi state.
"The new Iraqi prime minister is trying to do that but I think it is like trying to change the wheels on a moving car because the situation is so fluid."
He said claims that Saudi Arabia was partly to blame for the rise of IS - through funding of rebels fighting against President Assad - were "nonsense."
"I think there is a lot of commentary in the British press and the American press about Daesh and Saudi Arabia. Sometimes there is a simplification that they are two sides of the same coin, which is in my view, simply wrong."
On Saudi Arabia's record on human rights, Sir John said: "I'm not defending the flogging of bloggers and jailing of poets, but that happens elsewhere. If you want to talk about Saudi Arabia, you have a certain responsibility to come to see for yourself.
"When I talked to Saudi women in universities and elsewhere they would say the country will change but it will change at a pace of our choosing. And we don't want to force this pace - we need to do this along the contours of our own culture.
"A lot of people talk about women not being able to drive in Saudi Arabia, which is an issue, but funnily enough it's not really an issue for most Saudi women. The big issue is male guardianship. As a woman you need a male guardian to do all sorts of things."
Sir John said there is a lack of informed understanding about the Middle East.
"I don't think we have the depth of knowledge of these societies that we had in simpler times in the 1950s and 1960s."