More than 50 people have been arrested in “Iran-linked operations” in the past year in the UK and Jews are the target of “much of this aggression”, the head of MI5 has said.
In his annual threat assessment speech on Tuesday, Sir Ken McCallum said there had been increased Iranian action against Jewish sites, as well as a move towards harder targets such as military bases.
Russia was still “aggressor number one”, but Iran was “the other state keen on subcontracting its UK violence”, he explained.
He went on: “I've been calling this out since 2022. Today we continue to see familiar Iranian intent - using criminal proxies to intimidate oppositionists, Iranian media organisations and and Israeli sites.
“But 2026 has also seen the Iranians, like the Russians, attempting to expand their hybrid campaign.
“Over the last 12 months, our Iranian-linked operations have led to more than 50 arrests in the UK.
“Sadly much of this aggression has been aimed at British Jewish communities with whom I want to express solidarity.”
McCallum added: “The spring saw a wave of arson and sabotage incidents targeting Jewish communities in the UK and other European countries. These sickening acts, including against ambulances, synagogues and businesses were claimed by a group calling itself the Islamic Movement of the Companions of the Right.
"Behind this front sat members of IRGC. Both entities are now designated under the National Security Act giving us increased powers to disrupt and prosecute.
“What I can say is that is that those who would seek to cause mayhem on British streets - whether hired thugs or their paymasters overseas - will meet an unflinching response.”
During his speech, McCallum said: “Determined efforts have degraded the efforts of Islamic State but Al Qaeda and Islamic State continue to direct and inspire attacks.
“MI5 is still having to respond to attempts to carry out mass casualty attacks in the UK.”
He added: “Three Islamist extremists were convicted in February for planning to use automatic weapons against the Jewish community in Manchester.”
Speaking to journalists in a question and answer session after the speech, he said: “The RAF Fairford incident, which I won’t get further into for reasons you will understand, is not unique.
“There have been other examples not just in the UK but around the world, including more specifically in Iran’s own region.”
Sir Ken said that MI5’s state threats caseload has quadrupled in the past 10 years, adding: “In 2026, MI5 is devoting more resource to countering state threats than during the Cold War.”
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