The fatal moment predicted by Prince Bandar may now have come for many Shia, with Saudi Arabia playing an important role in bringing it about by supporting the notorious war fueled by ISIL foreign backed terrorists in Iraq and Syria. Since the capture of Mosul by the so-called Islamic State of Iraq and the Levant (ISIL) on 10 June, Shia women and children have been killed in villages south of Kirkuk, and Shia air force cadets machine-gunned and buried in mass graves near Tikrit. (However these crimes were also included the massacre of Iraqi Sunni and Christian civilians too).

In Mosul, Shia shrines and mosques have been blown up, and in the nearby Shia Turkoman city of Tal Afar 4,000 houses have been taken over by ISIL terrorists as "spoils of war".

There is no doubt about the accuracy of the quote by Prince Bandar, secretary-general of the Saudi National Security Council from 2005 and head of General Intelligence between 2012 and 2014, the crucial two years when al-Qaida-type militants took over the foreign-backed-armed opposition in Iraq and Syria. Speaking at the Royal United Services Institute last week, Dearlove, who headed MI6 from 1999 to 2004, emphasized the significance of Prince Bandar's words, saying that they constituted "a chilling comment that I remember very well indeed".

He does not doubt that substantial and sustained funding from private donors in Saudi Arabia and Qatar, to which the authorities may have turned a blind eye, has played a central role in the ISIL surge into Sunni areas of Iraq. He said: "Such things simply do not happen spontaneously." This sounds realistic since the tribal and communal leadership in Sunni majority provinces is much beholden to Saudi and Persian Gulf Arab regime paymasters, and would be unlikely to cooperate with ISIL without their consent.

Dearlove's explosive revelation about the prediction of a day of reckoning for the Shia by Prince Bandar, and the former head of MI6's view that Saudi Arabia is involved in the ISIL-led rebellion, has attracted surprisingly little attention. Coverage of Dearlove's speech focused instead on his main theme that the threat from ISIL to the West is being exaggerated because, unlike Bin Laden's al-Qa'ida, it is absorbed in a new conflict that "is essentially Muslim on Muslim". Unfortunately, Christians in areas captured by ISIL are finding this is not true, as their churches are desecrated and they are forced to flee. A difference between al-Qaida and ISIL is that the latter is much better organized; if it does attack Western targets the results are likely to be devastating.

The forecast by Prince Bandar, who was at the heart of Saudi security policy for more than three decades, that the 100 million Shia in the Middle East face disaster at the hands of a Saudi-led campaign to crush them.

Saudi sympathy for anti-Shia "militancy" is identified in leaked US official documents. The then US Secretary of State Hillary Clinton wrote in December 2009 in a cable released by Wikileaks that "Saudi Arabia remains a critical financial support base for al-Qaida, the Taliban, LeT [Lashkar-e-Taiba in Pakistan] and other terrorist groups." She said that, in so far as Saudi Arabia did act against al-Qaida, it was as a domestic threat and not because of its activities abroad. This policy may now be changing with the dismissal of Prince Bandar as head of intelligence this year.

The problem for the Saudis is that their attempts since Bandar lost his job to create an anti-Maliki and anti-Assad constituency which is simultaneously against al-Qaida and its clones have failed.

By seeking to weaken Maliki and Assad in the interest of other terrorist groups, Saudi Arabia and its allies are in practice playing into the hands of ISIL which is swiftly gaining full control of the opposition in Syria and Iraq. In Mosul, as happened previously in its Syrian capital Raqqa, potential critics and opponents are disarmed, forced to swear allegiance to the new faked caliphate and killed if they resist.

The West may have to pay a price for its alliance with Saudi Arabia and the Persian Gulf Arab monarchies, which have always found Takfiri militants more attractive than democracy. A striking example of double standards by the western powers was the Saudi-backed suppression of peaceful democratic protests by the Shia majority in Bahrain in March 2011. Some 1,500 Saudi troops were sent across the causeway to the island kingdom as the demonstrations were ended with great brutality and Shia mosques and shrines were destroyed.

An alibi used by the US and Britain is that the al-Khalifa royal family in Bahrain is pursuing dialogue and reform. But this excuse looked thin last week as Bahrain expelled a top US diplomat, the assistant secretary of state for human rights Tom Malinowksi, for meeting leaders of the main Shia opposition party al-Wifaq. Mr Malinowski tweeted that the Bahrain government's action was "not about me but about undermining dialogue".

Western powers and their regional allies have largely escaped criticism for their role in reigniting the war in Iraq. Publicly and privately, they have blamed the Iraqi Prime Minister Nouri al-Maliki for allegedly persecuting and marginalizing the Sunni minority, so provoking them into supporting the ISIL-led revolt. There is much truth in this, but it is by no means the whole story.

Maliki's failings are not the reason why the Iraqi state is disintegrating. What destabilized Iraq from 2011 on was the revolt of the opposition in Syria and the takeover of that revolt by Takfiri terrorist groups, who were often sponsored by donors in Saudi Arabia, Qatar, Kuwait and United Arab Emirates. Again and again Iraqi politicians warned that by not seeking to close down the civil war in Syria, Western leaders were making it inevitable that the conflict in Iraq would restart.

Of course, US and British politicians and diplomats would argue that they were in no position to bring an end to the Syrian conflict. But this is misleading. By insisting that peace negotiations must be about the departure of Assad from power, something that was never going to happen since Assad held most of the cities in the country and his troops were advancing, the US and Britain made sure the war would continue.

The chief beneficiary is ISIL which over the last two weeks has been mopping up the last opposition to its rule in eastern Syria.

Saudi Arabia has created a Frankenstein's monster over which it is rapidly losing control. The same is true of its allies such as Turkey which has been a vital back-base for ISIL and Jabhat al-Nusra by keeping the 510-mile-long Turkish-Syrian border open. As Kurdish-held border crossings fall to ISIL, Turkey will find it has a new neighbor of extraordinary violence, and one deeply ungrateful for past favors from the Turkish intelligence service.

As for Saudi Arabia, it may come to regret its support for the ISIL crimes in Syria and Iraq as ISIL social media begins to speak of the House of Saud as its next target. It is the unnamed head of Saudi General Intelligence quoted by Dearlove after 9/11 who is turning out to have analyzed the potential threat to Saudi Arabia correctly and not Prince Bandar, which may explain why the latter was sacked earlier this year.

The rise of ISIL is bad news for the Shia of Iraq but it is worse news for the supporters of this Takfiri group, whose leadership has been ceded to a pathologically bloodthirsty and intolerant movement, which has no aim but war without end.

(An opinion written by Patrick Cockburn issued by The Independent.)