The UK terror threat level has been reduced to severe from critical following what Amber Rudd, the home secretary, described as “good progress” in the investigation into the bomb attack on a London underground train that injured 30 people.
Military personnel who were mobilised when the the threat level was raised on Friday evening will return to normal duties, Rudd said. The decision was made by the independent joint terrorism analysis centre (JTAC) based at MI5 and means an attack is considered highly likely but is no longer “expected imminently”.
Announcing the decision Rudd urged the public to “continue to be vigilant but not be alarmed”.
“What it indicates is that good progress has been made,” she said. “[JTAC] has clearly decided that sufficient progress has been made to have the confidence but it is still an ongoing operation.”
She said there was no evidence that other explosive devices were in circulation, as had reportedly been claimed by representatives of Islamic State.
“They have always made claims that suit their own interests but actually there is no evidence of that,” Rudd said.
The Met assistant commissioner Mark Rowley, the national lead for counter-terrorism policing, said searches were continuing at addresses in Hounslow and Surrey but he said detectives “are getting a greater understanding of the preparation of the device”.
“There is still much more to do but this greater clarity and this progress has led JTAC to come to the judgment that an attack is no longer imminent.”
Late on Saturday police made a second arrest in the investigation and on Sunday searched a residential property in Stanwell, Surrey.
Police made a “significant” arrest of an 18-year-old man in the departure area of Dover port earlier on Saturday and he remains in custody under terrorism laws. Investigations also continued at a property in Sunbury-on-Thames following a raid by armed anti-terror police.
About 60 homes in the area were temporarily evacuated “as a precaution”. The address is believed by investigators to be connected to the making of the explosives that partly detonated at Parsons Green at 8.20am causing flash burns to some passengers and a stampede that injured others.
Residents said the property in Sunbury-on-Thames being searched by police was occupied by an elderly married couple known for fostering many children and young people over several decades and in 2010 were made MBEs.
Ronald Jones, 88, and his wife, Penelope, 71, who were honoured for services to children and families, are said to be staying with friends following the police raids.
One friend, Alison Griffiths, said the couple had been foster parents for almost 40 years and had taken in up to 300 children, including eight refugees, and had an 18-year-old staying with them recently.
Police scaled back the cordon around the property on Sunday and told residents there were no safety risks caused by the ongoing investigations. An inner cordon of 10 houses remained in place.
A 21-year-old man was arrested in Hounslow, west London, at about 11.50pm on Saturday in connection with the explosion at Parsons Green station, the Metropolitan police said.
The man was detained under section 41 of the Terrorism Act and taken to a police station in south London where he remained in custody on Sunday, Scotland Yard said.
Rowley said the travelling public would on Monday morning still see a high level of policing presence armed and unarmed.
“The military support we have had in place under Operation Temperer will start to phase out as we move through the coming week,” he said. “There are detailed and well-rehearsed plans in place to ensure a smooth transition from Operation Temperer, and military personnel will remain at readiness to deploy in support of the police should future security situations require.”
Counter-terrorism officers are leading the investigation supported by MI5. A key strand of the investigation has focused on CCTV to establish where, when and by whom the device, which is understood to have been fitted with a timer, was placed on the train.
Speaking earlier on Sunday Rudd said it appeared the bomber was not a lone wolf but that it was “too early to reach any final conclusions on that”.
While the arrest on Saturday of the 18-year-old was instantly hailed by police as “significant”, they are less sure about the importance to the attack of the person arrested in Hounslow. Investigators remain open-minded about whether one or more people was involved and have not yet found definitive evidence of a wider conspiracy.
The teenager arrested at Dover is suspected to have planted the device on the tube carriage, which was detonated by a timer, and would have caused much more extensive casualties had it fully exploded. Investigators do not believe the person who placed the home-made bomb on the train was present when it exploded.
Rudd said £24m of new government money was going towards counter-terrorism operations across the country.
Asked if police cuts had hit anti-terror operations, she said: “I think it is too simple to approach it like that. “What we have is an onslaught of attacks from Daesh trying to radicalise people.”