The incompetence of MI5 in failing to prevent Salman Abedi detonating his bomb at the Manchester Arena in 2017 beggars belief. According to Sir John Saunders, who chaired the inquiry into the Islamist atrocity which killed 22 people, a better response from MI5 ‘might have prevented the attack’.

In publishing his 226-page report, Sir John did not spare the intelligence service for missing several opportunities to thwart Abedi, who made little attempt to conceal his extremist ideology. MI5’s most calamitous mistake was to sit on a piece of intelligence that they received, information which has not been disclosed for national security reasons.

The first MI5 officer to assess the intelligence failed to discuss it with colleagues and did not write a report on the same day as was standard procedure. When the MI5 officer did eventually write the report, noted Sir John, it ‘did not contain sufficient context’.

Had the officer acted with more diligence, it is likely that Abedi’s return to the UK from Libya on May 18, 2017 ‘would have been treated extremely seriously by the Security Service’. Four days later Abedi blew himself up at the Manchester Arena.

Andrew Roussos, whose eight-year old daughter, Saffie-Rose, was the youngest victim of the attack, said on Thursday: ‘The fact that MI5 failed to stop him despite all of the red flags available demonstrates they are not fit to keep us safe and therefore not fit for purpose.’

This is not the first time that MI5’s ineptitude has been exposed by Islamist terrorists. There are many alarming similarities between the Manchester suicide bombing and the London attack in July 2005, that killed 52 people on the capital’s transport network. The inquest into that atrocity heard that two of the four homegrown bombers had come to the attention of MI5 earlier in 2005 but for reasons they refused to disclose at the inquest they decided not to investigate a crucial piece of intelligence.

As I wrote in an article for Coffee House in 2021, ‘ineptitude and complacency have characterised much of British intelligence’s battle against Islamic extremists’. As far back as the late 1990s, French intelligence agents christened the British capital ‘Londonistan’ because of the large numbers of extremists who had been allowed to set up home.

One was the Algerian Rachid Ramda, wanted by France for financing a series of attacks in Paris in 1995. The French newspaper, Le Monde, wrote that Jack Straw, Home Secretary at the time, ‘wanted to preserve London’s safe haven for Islamist militants’ in the hope it would prevent any terrorism attacks in Britain. On nine occasions the French government applied for his extradition but it was only after the 2005 London attack that Britain finally sent Ramda to France, where he was sentenced to life imprisonment.

Another was Abu Hamza, the Egyptian cleric, who for many years at the turn of the millennium preached hatred against Britain and the West from the Finsbury Park mosque. Among the people who regularly visited Hamza at the Mosque were one of the London suicide bombers and Richard Reid, who attempted to blow up a passenger jet with a shoe bomb in 2001. Muslim trustees of the mosque contacted police seven times to express their concern about Abu Hamza, but no action was taken.

The Americans were not so lackadaisical, and in 2004 they demanded Hamza’s extradition to face a series of terrorist charges; he was jailed for life in 2014.

Five years later a former French security advisor turned commentator, Alexandre Del Valle, recalled a conversation with an MI5 agent in 1997, in which the latter boasted that hosting Islamists ‘allows us to know who is who and guards us against terrorism’.

Has that deadly brew of arrogance and naivety been further addled in recent years by political correctness? William Shawcross’s courageous report last month about the risible anti-extremist Prevent programme laid bare the extent to which political correctness, particularly the fear of being labelled ‘Islamophobic’, was stymying Britain’s effort to tackle Islamic extremism.

In a speech on Wednesday the Home Secretary Suella Braverman admitted: ‘We have a blind spot in the system. It has allowed certain Islamist groups to operate under our radar. There can be no place for political correctness in our national security. In fact, I’d like to banish it altogether.’

A good start would be to forbid MI5 from any more virtual signalling nonsense, such as flying the Progress Pride flag above its HQ, which it did in 2021, just days after the inquest into the murder in 2019 of two people at Fishmonger’s Hall by Usman Khan. That inquest concluded that the police and MI5 were guilty of ‘serious deficiencies’ in their monitoring of Khan, a convicted terrorist. Relatives of the victims accused the intelligence services of avoiding responsibility for their failings by hiding ‘behind the cloak of secrecy’.

After Abu Hamza was arrested in 2004 he told a British court that he had MI5 to thank for his years of liberty at the Finsbury Park mosque. On one occasion one of their officers explained to him: ‘You have freedom of speech. You don’t have to worry as long as we don’t see blood on the streets.

How much more blood needs to be spilled on British streets before MI5 is shaken out of its complacency?