The Iran-linked incident at RAF Fairford is “not unique”, the head of MI5 said, as the regime moves towards harder targets such as military sites.

Iran, along with Russia and China, has been identified as a hostile state that uses proxies to carry out attacks on UK soil.

More than 50 people have been arrested in “Iran-linked operations” in the past year in the UK, which has seen a series of arson attacks on Jewish sites in London, and an alleged terror plot by two Iranian men on a synagogue in Manchester.

Following the incident at RAF Fairford, where three vans were stopped near the base, seven people were arrested and bailed by counter-terrorism police.

In his annual speech on Tuesday, the head of MI5 Sir Ken McCallum said the past year has seen increased Iranian action against Jewish sites, as well as a move towards harder targets such as military bases.

He said: “Those who seek to cause mayhem on British streets – whether hired thugs here or their paymasters overseas – will meet an unflinching response.”

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.”

Russia remains the “number one aggressor” and “continues to lash out at the UK and its allies,” he said.

“It’s worth clocking why these things are happening.

“It’s no accident that Russian aggressors are trying to unsettle other European homelands at a time when their military progress in Ukraine is minimal and horrifically costly.”

Turning to China, Sir Ken said the UK should pursue relationships with China that are in the national interest, but be aware of the potential risks of espionage.

In recent weeks MI5 took the unusual step of warning academics to cut ties with the China General Technology Research Institute, which it says is linked to the Chinese intelligence service.