Thirty-one late-stage attack plots were disrupted over the past four years by intelligence officers, the director general of the MI5 has said.

       MI5 director general Ken McCallum said that the threat of terrorism in the UK remains “a real and enduring thing” and warned that recent events in Afghanistan could lead to a new 9/11-style attack plot.

       He added: “We do face a consistent global struggle to defeat extremism and to guard against terrorism - this is real problem.”

       He told the BBC’s Today programme on Friday: “In the last four years, working with the police, my organisation has disrupted 31 late-stage attack plots in Great Britain.

       “That number includes mainly Islamist attack plots but also a growing number of attack plots from right wing terrorists.”

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       Mr McCallum said that the threats had not been diminished by the coronavirus pandemic.

       He revealed that “even during the pandemic period, which we have all been enduring for the past two years, we have had to disrupt six late-stage attack plots.

       “So, the terrorist threat to the UK, I am sorry to say, is a real and enduring thing.”

       Speaking about the impacts of the Taliban’s take-over of Afghanistan, Mr McCallum said: “The big concern, flowing from Afghanistan, alongside the immediate inspirational effect, is that terrorists re-constitute and once again cause us more in the way of well developed, sophisticated plots of the sort that we faced in 9/11 and the years thereafter.”

       With the 20th anniversary of 9/11 on Saturday, Ken McCallum reflected on where he was when the planes hit the twin towers. He said: “I was working as what we call an ‘agent runner’, working with human sources inside terrorist organisations in Northern Ireland.

       “On the morning of 9/11, or the lunch time as it was in the UK, when the first plan struck the twin towers we turned on the television in the corner of a room.

       “As the second plan struck, a colleague quietly said: ‘Osama Bin Laden’, and someone else said: ‘I guess we all know what we’re doing for the next ten years of our lives’ and so it proved.”

       Asked if he knew who Osama Bin Laden was at the time of the terrible attacks, Mr McCallum responded: “Yes, absolutely.”

       “We had been watching the rise of these Islamist extremist threats for some time,” he added. “Obviously Al-Qaeda had struck the US embassies in East Africa in 1998.

       “We’d seen attacks in Yemen in the year 2000. And something that is often forgotten is that in the UK, ten months before 9/11, we disrupted with the police a bomb plot in Birmingham. [It was] not formerly by Al Qaeda the organisation but this wave of terrorism was already coming towards us.”

       The director general said that the recent events in Afghanistan would not dramatically change terrorists’ capabilities overnight. But he said there would be a “psychological boost, morale boost” to extremists who were already residing in this country or other countries.

       He said that there could be a potential “re-growth” of “Al-Qaeda style directed plots” of the type that we saw several years ago.

       He added: “There is no doubt that recent events in Afghanistan will have heartened and emboldened extremists, and so being vigilant to precisely those kinds of risks is what my organisation is focused on.”

       Describing how the terrorist threat had changed over the past decade, Mr McCallum reflected that although the number of plots MI5 disrupts now is higher than it was directly after 9/11, they are “smaller plots of lower sophistication.”

       He explained that the so-called Islamic State had achieved something Al-Qaeda hadn’t by managing to inspire lots of people with no direct connection to the organisation to take their online instructional material and attempt much smaller scale plots.

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       He said these were “by their nature harder to detect”.

       Mr McCallum also compared terrorist threats to the challenges posed by foreign state-run spying campaigns. He said terrorism remained the biggest threat to life but that these “more insidious state-run threats” aimed to interfere in “our way of life” and “our democracy”.