MI5 Director-General Sir Ken McCallum has warned that terrorists are seeking to use artificial intelligence to improve attack planning, including through AI-enabled drones.

In his annual speech at the Security Service's Thames House headquarters in London, McCallum said MI5 had "caught terrorists seeking to exploit AI to improve their reconnaissance and attack methodologies, with AI-enabled drones adding a new twist". He described AI as "supercharging" the "contest between attackers and defenders" and warned that it could give less sophisticated groups access to capabilities previously beyond their reach.

"My adrenaline thresholds are set pretty high. I'm not easy to alarm, and neither is my organisation. But we are clear that, just as the benefits of AI are real, so are the national security risks," he said. "One concern would be that comparatively low sophistication actors may have a capability uplift in the AI era if these guardrails do not function as intended."

McCallum said he attached particular importance to the possibility of terrorists gaining capabilities involving biological or radiological weapons, adding that the government was taking additional steps to address the threat. "It has long been the case that many terrorists would dearly love to have some kind of capability around energy or biological or radiological weaponry. But that hasn't been easy for them to achieve," he said. He also warned about risks from AI itself, saying "human history has given us no experience of facing an actor which is smarter than we are".

McCallum announced an AI threat assessment centre within MI5, drawing on expertise from other British agencies.Turning to hostile state activity, he said Iran was increasingly targeting British military sites, describing the development as a "major shift" in its ambitions. Counter-terrorism police are investigating suspected Iranian involvement in an alleged plot at RAF Fairford after three suspicious vans were found near the base in the early hours of September 27. Five men were arrested.

The Prime Minister said on Monday that the alleged plot was "almost certainly" the work of Iran's Islamic Revolutionary Guard Corps. McCallum declined to discuss the investigation in detail but indicated that concerns extended beyond Fairford. "Do not draw inferences about any other specific incident when I say Fairford is not unique in the UK," he said. He said MI5's Iran-linked operations had resulted in more than 50 arrests in Britain over the past 12 months.

Russia, meanwhile, "remains aggressor number one", he said, citing sabotage, cyberattacks and a thwarted assassination plot in the United States. "You might be surprised to know that in 2026, MI5 is devoting more resource to countering state threats than during the Cold War," McCallum said. The service's hostile state caseload had quadrupled over the past decade, he added.

McCallum also addressed the recent increase in Britain's terrorism threat level to "severe", meaning an attack is highly likely. He said the change had been "driven in significant part by extreme Right-wing terrorism" linked to immigration. "Over the last year, the most marked trend has been an increase in cases where extremist versions of anti-immigration and anti-Muslim grievance are tipping into terrorist intent," he said. He revealed that an investigation into a 13-year-old in Britain who had been radicalised by extreme right-wing ideology helped disrupt a potentially lethal attack abroad several months ago.

With resilience as the theme of his address, McCallum urged the public to help strengthen Britain's defences against "malicious disruption and coercion". He cited attacks on American energy and water infrastructure, arson targeting European defence companies and "a destructive cyber attack on an energy generator" in Britain.

Calling for stronger community cohesion, he said "the cohesion and confidence of our communities has become a national security front line". Authoritarian regimes and other actors were "weaponising whatever frictions they notice", he warned. "Their trolls aren't geniuses, by the way; they only get a foothold if we give them one," he said.

McCallum also referred to the reported killing of Reform UK spokeswoman Ann Widdecombe as "part of a concerning trend of violence" against political figures. According to the report, Widdecombe, 78, was killed at her home in Haytor, Devon, in July. Joshua Kerry, 28, has been charged with her murder and preparing acts of terrorism, including against Reform UK leader Nigel Farage.