Armed police have smashed a suspected Islamic terror plot in a series of raids in West London and the Thames Valley.
Four men were arrested in a raids in west London and High Wycombe on suspicion of being concerned in the preparation and instigation of acts of terrorism.
One of the men, aged 27, was arrested by armed officers in a car in a west London street.
Police marksmen were also involved in two of the other raids raising fears that the suspects may have been armed.
There have been a series of arrests in London and other parts of the UK in recent weeks in connection with fanatics inspired by the militant Islamic State.
The fears have led to armed soldiers and police marksmen patrolling key buildings and sensitive areas in central London.
Scotland Yard said officers from the force’s Counter Terrorism Command carried out the arrests last night and early today.
The other men being held are aged 19, 22 and 25. All were taken to a central London police station for questioning.
Two of the entries to premises were assisted by firearms officers. No shots were fired.
Police said no shots were fired.
A number of residential addresses and vehicles are being searched by specialist officers in west London and Thames Valley as part of the investigation.
The Yard issued a statement saying : “These arrests and searches are part of an ongoing investigation into Islamist related terrorism.
“Officers from the Metropolitan Police Service's Counter Terrorism Command (SO15) are working closely with their colleagues in the SE Counter Terrorism Unit and MI5.
“The searches are ongoing, enquiries continue.”
No further details of the arrests were released for what the Met described as "operational reasons."
The raids come a few months after the national terror threat level in the UK was raised from substantial to severe, meaning a terrorist attack is "highly likely". This assessment is separate from the evaluation concerning police officers.
The threat level was raised against a backdrop of increasing concerns over hundreds of aspiring British jihadis travelling to Iraq and Syria to learn terrorist "tradecraft" and fight alongside terror groups such as Islamic State.
There are fears that some of those returning home may attempt to carry out attacks in London.