Home Secretary Yvette Cooper thanked police for disrupting among “the biggest counter-terrorism threats seen in recent years” after eight men were arrested in two separate investigations that both involved Iranian nationals.
Five males, including four from Iran, had been held at locations across England on Saturday on suspicion of preparation of a terrorist act.
The suspected attack was “hours away” from being launched, according to the Telegraph.
Sources told the Mail that the plot was a “major attack’” that could have led to an imminent threat to life.
While an expert said it was “highly likely” elite soldiers from the SAS joined counter-terror cops and MI5 in foiling the alleged plot.
Scotland Yard and the security services uncovered a suspected plot to target a single premises.
The force confirmed a further three Iranian men were arrested on Saturday as part of a separate operation.
Metropolitan Police detectives have been in contact with the site in the first plot to make them aware and to provide relevant advice and support but it has not been identified for operational reasons, a spokesman said.
Ms Cooper said: “These were two major operations that reflect some of the biggest counter state threat and counter terrorism operations that we have seen in recent years.
“I want to thank the police and security services who showed the most impressive professionalism and expertise in carrying out these operations to keep the country safe.
“We support the police and the security agencies in the ongoing work that they are doing. The most important thing is to protect our national security.”
Asked about possible links to the Iranian state, she said: “These are major operations that have taken place and the ongoing investigation is immensely important, and of course it involves Iranian nationals in both investigations and we are supporting the police and the security agencies in the investigations that they are taking and the security assessments that they are doing.
“But this reflects the complexity of the kinds of challenges to our national security that we continue to face that we have set out and that is why protecting our national security including supporting these extremely professional operations and investigations remains our top priority.”
Dominic Murphy, the Met Police’s head of counter-terrorism, said one was a plot for an attack against a specific premises, while the other was a national security arrest.
He said the force made all the arrests they are seeking to – but several hundred officers are still working on the investigations, which are in their early stages.
A series of arrests made yesterday, as part of @TerrorismPolice operations, marked some of the largest counter state threat and counter terrorism actions seen in recent times.
— Home Office (@ukhomeoffice) May 4, 2025
Watch Home Secretary @YvetteCooperMP's message. pic.twitter.com/xlEwEm2ole
Police are not treating the two cases as linked and Mr Murphy asked the public to “avoid speculation and some of the things that are being posted online”.
He told Sky News it was “unusual for us to conduct this scale of activity”.
Colonel Philip Ingram, who served in British military intelligence, told MailOnline: "It's distinctly possible that - with this given a national level of threat and with hostile state links - there could be SRR troops from a surveillance perspective and they could have brought in special forces operatives as a backup team for counter terror police.
"There's a strong possibility given the multifaceted nature of the threat that counter terror could have been working with UK special forces."
Col Ingram said it was "rare" for the military to be involved in supporting police operations but not unprecedented.
The first four Iranians were arrested on suspicion of preparation of a terrorist act, contrary to section 5 of the Terrorism Act 2006, and the fifth man, whose nationality is yet to be established, was detained under the Police and Criminal Evidence Act.
Those arrested include a 29-year-old man in the Swindon area, a 46-year-old man in west London, a 29-year-old man in the Stockport area, a 40-year-old man in the Rochdale area and a fifth man in the Manchester area. They remain in custody.
Another three Iranian men were arrested at three addresses in London as part of a separate counter-terrorism operation under section 27 of the National Security Act 2023.
Section 27 grants constables the power to arrest individuals without a warrant if they reasonably suspect them of being involved in “foreign power threat activity”.
Two men, aged 39 and 44, were arrested at separate addresses in north-west London and the third – a 55-year-old man – was held in west London. They remain in custody.
The head of MI5, Ken McCallum, said in October that authorities had stopped 20 state-backed plots hatched by Iran in the UK since 2022.
He warned of an “unprecedented pace and scale” of plots posing “potentially lethal threats” to British citizens and UK residents.
Iran was the first foreign power to be listed on the enhanced tier of the foreign influence registration scheme (Firs), aimed at protecting the UK from malign foreign influence.
It means anyone who is directed by Iran to carry out activities in the UK must declare it or face five years in prison.
The scheme is due to come into force in July.
A resident of Rochdale said he saw counter terrorism officers raid a neighbouring property after his kids ran inside from playing in the garden.
“We heard a massive bang and saw loads of police everywhere with guns shouting at us to get inside the house,” Kyle Warren told Sky News.
“We went inside and went upstairs to see what was going on.
“Then we saw a man getting pulled out from the back, he basically got dragged down the side entry and thrown into all the bushes and then handcuffed.
“There must have been 20 to 30 police officers.”
