MI5 is devoting more resources to countering state threats than during the Cold War, the security service's Glasgow-born chief has said, as he warned that Iran-linked operations targeting the UK are becoming increasingly concerning.
Sir Ken McCallum said the service's state threats caseload had quadrupled in the past decade, with hostile states including Iran, Russia and China using proxies to carry out activities on British soil.
Annual speech highlights growing threats
Speaking during his annual speech on Tuesday, he said MI5 was now dedicating more resources to countering state threats than at any point during the Cold War.
He said: "In 2026, MI5 is devoting more resource to countering state threats than during the Cold War."
His comments come after seven people were arrested and bailed by counter-terrorism police following an incident involving three vans stopped near RAF Fairford.
Iran-linked operations and arrests
Sir Ken said the incident was "not unique", amid growing concerns about Iranian activity targeting Jewish sites and a shift towards harder targets, including military installations.
More than 50 people have been arrested in Iran-linked operations in the UK over the past year, against a backdrop of a series of arson attacks on Jewish sites in London and an alleged terror plot involving two Iranian men targeting a synagogue in Manchester.
Speaking to journalists after his speech, Sir Ken declined to discuss the RAF Fairford incident in detail but said similar incidents had occurred in Britain and elsewhere around the world.
Firm response promised
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."
During his speech, Sir Ken warned that those involved in attempts to cause disruption in Britain would face a firm response. He said: "Those who seek to cause mayhem on British streets, whether hired thugs here or their paymasters overseas, will meet an unflinching response."
Sir Ken said the past year had seen increased Iranian activity against Jewish sites, alongside a move towards targeting more challenging locations such as military bases.
Russia and China concerns
Russia remains the "number one aggressor", he said, accusing the country of continuing to target 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 Britain should continue to pursue relationships with the country where they served the national interest, while remaining alert to the 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 the security service says is linked to Chinese intelligence.
