MI5 Chief: Russia, Iran and AI Now Equal Terrorism Threats to UK

Sir Ken McCallum stood before an audience in London and delivered a stark recalibration of British security priorities. The head of MI5 announced that the intelligence service now devotes more resources to countering state threats than it did during the entire Cold War—a seismic shift in how the country allocates its defensive capacity. The work of tackling terrorism and state-level aggression, he said, had reached roughly equal scale, a reordering that reflects a decade in which threats from foreign adversaries have quadrupled.

Russia sits at the center of this new calculus. McCallum named it "aggressor number one," describing a campaign of hybrid warfare—cyber-attacks, sabotage, disinformation—designed to unsettle European nations without crossing into conventional military conflict. The Kremlin has stopped short of direct confrontation with NATO, he noted, while its full-scale invasion of Ukraine grinds forward at minimal territorial gain and horrific cost. What makes Russia's position precarious, in McCallum's assessment, is the damage already inflicted on its traditional espionage apparatus. Nearly 1,000 Russian spies have been expelled from the UK since the invasion began, leaving Moscow dependent on paying proxies and criminals to carry out operations on its behalf. "These are not the actions of a great power with the strategic upper hand," McCallum said.

Iran has mounted its own escalating campaign across British territory. In the past year, MI5 recorded 50 arrests linked to Iranian activities, much of it directed at Jewish communities and military installations. The incident at RAF Fairford in Gloucestershire—where three suspicious vans were discovered near the airbase—exemplifies this pattern. Seven people were arrested and bailed by counter-terrorism police in connection with that case. Prime Minister Andy Burnham has said the incident was "almost certainly directed by Iran's Islamic Revolutionary Guard." McCallum confirmed the airbase was not an isolated target. "We have seen Iranian interest beyond RAF Fairford in the UK," he told reporters.

The emerging threat landscape now includes artificial intelligence in ways that complicate both attack and defense. Extremist groups have already begun exploiting AI to sharpen their reconnaissance, refine attack methodologies, and integrate the technology with drones. MI5 has caught terrorists attempting precisely this. The more distant but graver concern is bioweapons. McCallum warned that AI has the potential to enable the development or modification of biological weapons, though he stressed this threat has not yet materialized. "Put at its simplest, human history has given us no experience of facing an actor which is smarter than we are," he said, acknowledging the unknowable dimensions of the risk. To address this, MI5 has established an AI Threat Assessment Centre tasked with separating credible threat from speculation.

Domestic terrorism remains a persistent pressure point, and the character of that threat has shifted. In April, the UK raised its terrorism threat level to severe for the first time in five years, signaling that an attack is highly likely. Islamist groups including Al Qaeda and Islamic State continue to direct and inspire attacks. But the most marked trend over the past year has been the rise of extreme right-wing terrorism. McCallum described a pattern in which anti-immigration and anti-Muslim grievances are tipping into terrorist intent. This category of threat skews young and spreads through the internet. MI5 recently investigated a radicalized 13-year-old in the UK; that investigation yielded intelligence that enabled an international partner to prevent a lethal attack on their soil.

When asked about Prime Minister Burnham's recent assertion that Russia interfered with the Brexit referendum, McCallum acknowledged it as established fact but drew a careful distinction. Russian media outlets, internet trolls, and bot farms had attempted to influence the 2016 referendum debate—that is public record. But he emphasized the referendum result itself was not in dispute and expressed concern that overplaying Russian interference could inadvertently amplify the reach of those operations. "I am a little bit anxious that we don't play into our adversaries' hands by making these trolls look 10ft tall," he said.

The National Security Act, passed in 2023 to target individuals working against UK interests on behalf of foreign powers, has become a heavy-use tool in this expanded security architecture. It has been deployed against threats from Russia, Iran, and China alike. McCallum's message was unambiguous: "Those who seek to cause mayhem on British streets—whether hired thugs here or their paymasters overseas—will meet an unflinching response." The rebalancing of MI5's resources, the identification of state actors as co-equal threats to terrorism, and the acceleration of AI-enabled risks all point toward a security environment fundamentally different from the one that prevailed even five years ago.