london —
Post-Cold War stability has been replaced by a “more contested era” and Britain has entered a new phase of national security, the head of internal security agency MI5 said on Tuesday, warning that threats from state and terrorist attacks could be further enhanced by artificial intelligence.
Ken McCallum has called on the UK to be more resilient and vigilant, warning that the country faces a “new era of national security” as it fends off the combined threat of Russia, Iran and China.
In his annual address outlining the threats facing the UK, he said: “These days our operational missions against terrorism and state threats are of almost equal size, which in itself is a big change in recent years.”
These threats can take many forms, including “arson, sabotage, cyberattacks, coercion (and) violence,” McCallum said.
In announcing the creation of the new AI Threat Assessment Center, McCallum said AI was “already enhancing” some of these threats, particularly in cybersecurity. He also warned that the technology could enhance the capabilities of “relatively sophisticated and low-skilled attackers” if governments do not put enough “guardrails” around it, adding that most worryingly, AI has the potential to help create destructive biological weapons, but this has not yet been realized.
Mr McCullum reiterated previous warnings, emphasizing that the threat posed by the state is now the service’s main focus. “You may be surprised to learn that in 2026, MI5 will be dedicating more resources to countering national threats than during the Cold War,” he said. “Over the past decade, the number of incidents of state intimidation has quadrupled,” he said, warning that the new heightened threat environment is not a “temporary phenomenon.”
“Russia remains the number one aggressor,” says MI5 chief.
Of these countries, “Russia remains the primary aggressor,” McCallum said, pointing to Russia’s escalating “hybrid warfare” operations targeting European countries. He cited as examples a cyberattack on Poland’s energy infrastructure and an attempt to “destroy a German cargo plane using explosive-laden drones.”
In the UK, “a man was charged under the National Security Act last month for allegedly preparing to sabotage a drone factory in Swindon,” McCallum added.
Still, these are not the “actions of a strategically advantaged great power,” McCallum said, noting that Russia’s espionage capabilities have been significantly reduced since it launched a full-scale invasion of Ukraine in 2022, when more than 1,000 foreign staff were expelled from their host countries. Instead, Russia is busy “paying criminals to do their bidding,” McCallum said.
Iran has also used similar techniques to “expand its hybrid operations,” he added. He said more than 50 people had been arrested in connection with Iran-related plots, most of which were directed against Britain’s Jewish community.
MI5 chief McCallum says more than 50 people have been arrested in the UK in connection with Iran-related operations
McCallum also referred to “Iran’s ambitions to go after more difficult targets, such as military sites,” alluding to last month’s incident at Fairford Air Force Base. He declined to provide further details because the investigation is ongoing, but said the Fairford case was “not unique.”
“There are other examples, not just in the UK but around the world,” he added.
British Prime Minister Andy Burnham said Iran’s Islamic Revolutionary Guard Corps was “almost certainly” responsible for orchestrating the alleged plot to target a Royal Air Force base used by US forces. Several Iranian officials have vehemently denied these accusations. Several men, including a dual British-Iranian national, were arrested in connection with the plot and later released on bail.
Shortly after the incident, the United States made the unusual decision to return all long-range bombers stationed in the United Kingdom to their home base on the American mainland in response to unspecified new threats.
Mr McCallum also accused China of spying in the UK, citing MI5’s warning to academia two weeks ago and an incident earlier this year that resulted in the “first-ever conviction for national security crimes” linked to China.
While stressing the growing role of the state, he said terrorism “remains the number one concern for MI5” and that “an attack is very likely to occur”.
