The head of MI5, Sir Ken McCallum, has said that Iran is expanding its attempts to strike harder targets, including military facilities in the United Kingdom, while Russia continues to escalate its hybrid warfare against Ukraine’s allies.
Speaking during his annual threat assessment at MI5 headquarters (Thames House) in London, McCallum described a “significant shift” in 2026 in “Iranian ambitions to come at harder targets, such as military sites.” He said the incident at RAF Fairford “is not unique,” adding that there have been other examples both in the UK and around the world.
The day before, Prime Minister Andy Burnham told Parliament that a suspected plot against RAF Fairford — a base previously used by US bombers to carry out strikes on Iran — was “almost certainly” coordinated from Iran and directed by the Islamic Revolutionary Guard Corps (IRGC). Following the incident in late September, when several British citizens were detained near the base’s perimeter, the United States withdrew its aircraft from the site. Iran has denied any involvement.
McCallum stressed that over the past year, MI5 operations linked to Iran have led to more than 50 arrests. A significant portion of Iranian activity has been directed against Jewish communities in the UK, as well as against military sites. The spy chief noted that Tehran, like Moscow, is increasingly relying on criminal proxies to carry out operations.
McCallum once again described Russia as “aggressor number one.” In his assessment, Russian military and intelligence services are escalating hybrid actions while remaining below the threshold that would trigger a collective NATO response. He cited a cyber-attack on Polish energy infrastructure and an attempt to use an explosive-laden drone against a cargo plane in Germany as examples. The MI5 chief added that after the expulsion of nearly 1,000 Russian spies and diplomats following the full-scale invasion of Ukraine, the Kremlin has been forced to rely on criminals and naïve operatives — “these are not the actions of a great power with the strategic upper hand.”
McCallum also said that state threats have quadrupled over the past decade, and that MI5 is now devoting more resources to countering them than it did during the Cold War. Operations against terrorism and state threats have become roughly equal in scale. He warned of a “new era of national security” and of risks linked to AI, including the potential use of the technology to develop biological weapons.
