NATO’s decision to launch a ferocious bombing campaign to help Islamist rebels overthrow Colonel Gaddafi in 2011 hangs over Britain today like a toxic cloud. For the Manchester bomber, Salman Abedi, hailed from a Libyan family accused of being aligned to one of the many jihadist movements in that country.

The strategy to send in the RAF against Gaddafi’s forces was most enthusiastically promoted, to his eternal shame, by then Prime Minister David Cameron. His reckless policy brought about regime change as the Islamists came to power, along with their violent henchmen.

As was the case with opposition groups in Tunisia, Egypt and Syria before the so-called Arab Spring, those who were set against Gaddafi’s rule were extreme in their ideology, blinded by a hatred of secularist, non-religious governments.

Clueless: Beaming David Cameron in Libya after the fall of Gaddafi in 2011

But despite all evidence to the contrary, Cameron and his deluded European partners lied to us that they were actually pro-democracy Western allies, champions of tolerance and plurality.

Some of us — including me and other Middle East experts writing for this paper — warned repeatedly that their agenda was far more sinister, and we would pay a terrible price for Cameron’s naivety.

For those of us who had studied the history and lived in the region, it was obvious that, despite their internal divisions and rivalries, all those disparate jihadist groups in Libya had one overriding and very dark ambition: to replace Gaddafi’s secular regime with one based on their own mercilessly hardline interpretation of Sharia law, before seizing the country’s oilfields and finally cutting all ties with Western countries they openly despised.

For this reason, the groups had been banned and their members ruthlessly persecuted by Gaddafi and other secular Arab leaders, and they were viewed with deep suspicion in the West — with one notable exception.

The British government welcomed Salman Abedi’s father Ramadan into our country with open arms in 1993 as part of a reckless liberal policy of granting political sanctuary to Islamist activists from Libya and other Arab nations.

'Mr Cameron had neither understood nor considered the aftermath of enforced regime change'

The misguided belief was that they would warm to the host nation that offered them sanctuary, and modify their opinions through the new experience of living in an open democracy.

Instead, many of them not only continued stirring up rebellion in the countries they came from, but called openly for Islamist rule in their adopted homeland. Successive British governments turned a blind eye to this treachery.

And finally, after being given refuge here to cultivate their hatred of everything we hold dear, the Islamists found the perfect dupe in David Cameron as they sought to fulfil their dream of creating an Islamist state in Libya.

Salman Abedi’s father returned to Libya in 2011 to fight alongside Al-Qaeda-affiliated forces against Gaddafi, supported by Nato airstrikes. After Gaddafi was killed, the Abedi family spent more time in Libya.

Thanks to Cameron, they could at last immerse themselves in what was now a blood-soaked, chaotic country with no functioning government, awash with arms seized from abandoned Libyan Army depots and mired in tribal and religious upheaval which each day left hundreds of corpses lining the streets. And it was one where the Islamists were about to emerge triumphant.

Astonishingly, it was at this juncture that Cameron travelled to Libya to glory in his great ‘victory’, hailing the dawn of a new democratic era before abandoning it to a chaotic, impoverished and blood-soaked fate.

Like Tony Blair in Iraq, he had neither understood nor considered the aftermath of enforced regime change.

Shell-shocked Libyans were bequeathed a new and terrifying reality by Cameron and his Nato allies, as Libya became a breeding ground for Islamist terror.

In some ways, the consequences of that have culminated in the Manchester bombing. For this insanely ungovernable Libya is where Salman Abedi, paying frequent visits to his family, was able to cultivate his murderous hatred of the West.

(We now learn, too, that his father is said to have fought with a group linked to Al-Qaeda, and his younger brother is alleged to have Islamic State connections.)

That loathing for our values came to a horrifying climax this week, just days after he travelled back to Manchester from Libya.

The benighted country has taken on a growing significance for Islamist jihadis as the self-declared caliphate of Islamic State in Syria, and Iraq has gradually been overwhelmed by a Western coalition. Islamic State hoped to establish a new base in Libya, where Al-Qaeda also has a strong presence.

As Islamic State territory elsewhere shrank, thousands of jihadis fled towards Libya in the hope of establishing another Islamist redoubt, from where murderous attacks — like that which took place in Manchester — could be launched against Europe.

Jihadist leaders sought to forge a sort of corridor between Libya and Syria — where Cameron, as Prime Minister, was also itching to overthrow secular dictator Bashar Al-Assad, while championing the cause of non-existent ‘moderate’ rebels.

This corridor facilitated the flow of money, men and weapons between Syria and Libya.

'Manchester bomber Salman Abedi found himself immersed in a Libya fast becoming the new crucible of terror on Europe’s doorstep'

So it was that the Manchester bomber, Salman Abedi, found himself immersed in a Libya fast becoming the new crucible of terror on Europe’s doorstep.

Abedi — as part, it now appears, of a wider British-Libyan jihadi cell — was able to use the ‘jihadi corridor’ to travel between Libya and Syria and receive additional and extensive training in Syrian terror camps.

And his get-of-out-jail-free card? A prized British passport, which meant he could fly back to this country from Libya whenever he chose, free to unleash death upon his fellow citizens.

As well as the terrorists who now operate with impunity in Libya, the country has become a major arms-dealing hub and the centre of a massive smuggling operation in which hundreds of thousands of migrants have been sent across the Mediterranean in boats to flood into Europe virtually unchecked.

This, then, is Mr Cameron’s legacy — though Tony Blair must take some of the responsibility for unleashing chaos in Iraq by helping to topple Saddam Hussein, whose old generals were involved in the creation of Islamic State.

These revelations are a huge embarrassment for the political leaders and military strategists who orchestrated the Libya debacle in 2011. Our current Government and intelligence leaders should be furious they have been left to face the terrible consequences.

To say Cameron has the blood of the Manchester victims on his hands may be too stark a conclusion. What is indisputable, though, as our country remains on its highest state of terror alert and the remaining jihadi cell members are hunted down, is that if wiser heads than David Cameron’s had prevailed six years ago, the suicide bombing in Manchester would probably not have taken place.

John R. Bradley’s latest book is After the Arab Spring: How Islamists Hijacked The Middle East Revolts.