UK facing growing threat from Russia, Iran, and terrorists, MI5 chief says

China has been accused of cyber espionage and interfering in UK public life

Director General of MI5 Ken McCallum delivers the annual Director General's Speech at Thames House, the headquarters of the UK's Security Service, in London, Britain, Oct 16, 2025. Jonathan Brady/Pool via REUTERS

Britain is facing an escalating threat from hostile states such as Russia, Iran, and China while the terrorism risk is "huge" with al Qaeda and Islamic State seeking to incite would-be attackers, the UK's domestic spy chief said on Thursday.

MI5 Director General Ken McCallum said there had been a 35% increase in the number of people being investigated over state threat activity, saying hostile nations were consistently descending into the "ugly" methods usually employed by terrorists.

McCallum said his agency had disrupted "a stream of surveillance plots with hostile intent" from Russia and had tracked more than 20 potentially lethal Iran-backed plots.

"In 2025, MI5 is contending with more volume and more variety of threat from terrorists and state actors, than I've ever seen," he said in his annual speech at MI5's headquarters in London.

Britain has repeatedly spoken of hostile action which it says is carried out by Russia, Iran and China who all deny any of the accusations levelled in their direction.

Earlier this year, six Bulgarians were jailed for spying for Russia by carrying out surveillance on its behalf while five men were also convicted of carrying out an arson attack on Ukraine-linked businesses in London which British officials said had been ordered by Russia's Wagner mercenary group.

"With our partners across Europe, MI5 will keep detecting those who take orders from Russian thugs," McCallum said.

"And we will keep following the trails back to those giving the orders, who imagine they're anonymous and unfindable behind their screens. They're not."

He said China was guilty of cyber espionage, luring academics to China, interfering covertly in UK public life and the harassing of pro-democracy dissidents in Britain.

On Iran, he said Tehran was "frantically" trying to silence its critics around the world, and cited how Australia had exposed Iranian involvement in antisemitic plots and Dutch authorities had revealed a failed assassination attempt.

He also said the terrorist threat to Britain remained "huge" with MI5 and police disrupting 19 late-stage attack plots since the start of 2020.

"Al Qaeda and Islamic State are once again becoming more ambitious, taking advantage of instability overseas to gain firmer footholds," he said.