The Manchester and London bomb attacks are failures for British security but also prove that the jihadi assault in Europe has lost its way, according to the foremost French academic expert on Islamist terrorism.

Professor Gilles Kepel believes there is a “jihad fatigue” among many young Muslims who were once attracted to Isis.

“These kinds of attack — targeting children at a concert and people in the street and restaurants — are not going to gain new recruits and sympathisers.” he says. “They are terrible events and a calamity for British security but they are further signs that the Isis model… is going nowhere.”

“They show that individuals inspired, and possibly guided, by Isis are still capable of causing great harm but that the declared objective — to cause civil war in Europe — is likely to fail.”

Prof Kepel, 61, though sometimes controversial in his native France, has gained an international reputation as one of the most penetrating analysts of the Arab world, Islam and what he calls the “third generation” of jihadi attacks on the West. His influential 2015 book Terreur dans L’Hexagone, has just been published in updated and expanded form in English as Terror in France: The Rise of Jihad in the West, by Princeton University Press.

Prof Kepel, who holds the chair of Middle Eastern and Mediterranean studies at the prestigious Ecole Normale Supérieure in Paris, travelled to London to give a lecture on the day after the Manchester Arena attack which killed 22 people.

“In France, I have 24-hour security guards because I have received many death threats,” he says. “The British security services assured me that was not necessary. And then Manchester happened…”

Prof Kepel says that the Manchester attacker, Salman Abedi was a classical example of what he calls a “third generation” jihadi.

“He was born in Manchester. He graduated from a Manchester gang. He had an absentee father who had been involved with Libyan islamist fighters and was given refugee status in the UK. Salman Abedi was not sent from another country — like the 9/11 attackers. He was fighting on his own turf and probably picked his own target.”

Abedi, Prof Kepel said, typified the advantages — and the ultimate weaknesses — of the new model of Islamist terrorism which has assaulted western Europe in the last five years.

Because he was “home-grown” and apparently a small-time criminal, he passed under the radar of MI5 and the police. Because he was probably not under the specific orders of the Isis leadership, he picked a target which fitted radical jihadist hatred of western values and lifestyles but also one likely to reinforce a growing revulsion against Islamist violence among second-generation European Muslims.

Prof Kepel identifies the “first generation” of jihadi terrorism as the attacks against Muslim governments in Afghanistan and Arab countries in the 1990s. The second generation was the Al Qaeda model of well-funded attacks on mostly US targets, culminating in the 9/11 assault on the Twin Towers in New York.

Prof Kepel traces the birth of the “third generation” to a lengthy text placed online in 2005 by Abou Moussab al-Souri, a Syrian-born and French-educated theorist of jihad. Al-Souri declared that Al Qaeda had failed in its “top-down” plans to foment a global Islamic insurrection. He called instead for an attack on the “soft belly of the west” — western Europe, where there were thousands of second generation Muslims cut off from mainstream society.

Al-Souri called for a “system not an organisation”, which would inspire a new form of “low cost” terrorism conducted by young Muslims in their own cities. He believed there was an opportunity to capture the minds of young Muslim criminals by offering them a heroic, new start in the service of Islam.

“When I spoke to the authorities, including in Britain, they said this loose structure could never work,” Prof Kepel says. “They missed the fact that it coincided with the creation of YouTube and Facebook and other social media, which gave al-Souri’s idea a means of becoming reality. They messed up.”

Prof Kepel says that the Mohamed Merah killings in Toulouse in 2012 began a sequence of “third generation” jihadist attacks, including Charlie Hebdo and the Bataclan in 2015, Nice in 2016 and Manchester and London in 2017. Although Isis played a direct role in the Paris attacks, the Nice and Manchester atrocities were probably loosely inspired, rather than controlled, Prof Kepel believes. “As with Al Qaeda, the aim was to provoke an indigenous backlash against Muslims and foment a civil war. This has not happened,” Prof Kepel said. “The attacks on a Jewish school in Toulouse and on Charlie Hebdo magazine were accepted as legitimate by some Muslims, though not by the vast majority.”

“The switch to indiscriminate targets, like Manchester and now London has cut off much of this support. Why then choose such targets? They are easy and that points to a weakness inherent in the low-cost, bottom-up model. The operational decisions are not made by leaders but by local activists.”

The near-collapse of the Islamic State “califate” in the Middle East has also altered the mood in radical Islamic circles, Prof Kepel says. “If you looked at pro-Isis chat rooms a year ago, they were full of triumphalist stuff saying European women and children would be sold as slaves by a soon-to-be born caliphate in Europe. This kind of rubbish has vanished. The tone is now despondent. The feeling is that Isis is in dire straits and that a new model is needed.”

Prof Kepel says the recruitment sergeants of radical, violent jihad are no longer finding much of a response.

Will there be a “fourth generation” of jihad and, if so, what form will it take?

“That is what we don’t yet know and what we must study carefully,” he says. “We cannot afford to miss the signs again.”