Twenty-five years after the 9/11 attacks killed 2,977 people in the worst assault on American soil since Pearl Harbour, MI5 chief Ken McCallum has warned that Britain is facing a similarly significant shift in threats.
In his annual threat update speech, McCallum recalled that he was five years into his MI5 career when al-Qaeda struck the United States. Sixty-seven Britons were among the victims, but the ripple effects of that day—wars in Iraq and Afghanistan, and attacks reaching British streets—claimed thousands more lives.
From Northern Ireland to the war on terror
McCallum, who has led British counter-terrorism and espionage efforts for six years and served as an MI5 officer for three decades, described how 9/11 fundamentally reshaped the agency. The shift from focusing on Russian and Chinese espionage and Northern Ireland terrorism brought larger budgets and a new emphasis on fighting Islamist extremism.
Sources from that era say the pace of change was break-neck as MI5 recruited new officers, language experts, and agent insiders to infiltrate jihadist networks.
New era of threats
In his speech, McCallum acknowledged that “we’re there again,” describing a “seismic” transformation in response to evolving dangers. Beyond the persistent Islamist threat, he pointed to subversion and violence from Russian and Iranian states.
He warned that artificial intelligence could assist bad actors in advancing bio-warfare, while toxic internet messaging can be harnessed to incite division in UK society. Young people, he said, are being radicalised in ways unimaginable a quarter of a century ago.
Call to resist division
McCallum highlighted daily attacks on banking systems, underwater cables, critical infrastructure, and health systems—all below the threshold of war. His appeal to the British public to “think” about how they are being attacked and to reject division and hatred is a call to use persuasion and reason against state efforts to promote racism and resentment.
As MI5 officers battle terrorism in the shadows, they also fight against enemies interfering with the minds of citizens—a battle McCallum suggests may be the toughest of all.
