Terror: Man arrested over knife threat at Whitehall.

Officers swoop on man carrying bag with three knives

Security services have foiled an attempt to bring more terror to the heart of Westminster.

Police swooped on a man carrying a bag of knives in Whitehall and arrested him on suspicion of planning a terror attack.

It is understood the arrest of the 27-year-old suspect was “intelligenceled” and was made as part of a joint operation being carried out by MI5 and counter-terrorism police.

The circumstances of the swoop would suggest the suspect may have been under some form of surveillance prior to his arrest.

The bearded man, described as “very calm” by a witness, was carrying a rucksack containing at least three knives when he was detained yards from the scene of last month’s attack by Khalid Masood.

The Metropolitan Police said he was arrested yesterday “following a stop and search as part of an ongoing operation”, and was held at approximately 2.22pm by armed officers from the specialist firearms command.

Scotland Yard’s statement said: “The man, aged in his late 20s, was arrested on suspicion of possession of an offensive weapon and on suspicion of the commission, preparation and instigation of acts of terrorism.

“Knives have been recovered from him.

“He is being detained under the Terrorism Act and is in custody in a south London police station.

“Detectives from the counter terrorism command are continuing their investigation and, as a result of this arrest, there is no immediate known threat.”

Dressed in dark clothing, the suspect was wrestled to the ground on a traffic island at the Parliament Square end of Whitehall, close to the Foreign Office and the entrance to Downing Street.

Handcuffed, with his arms behind his back, one of his hands appeared to be wrapped up in a bandage as four officers stood next to him.

Images from the scene showed three knives on the ground close to a brown rucksack, and an officer in forensic overalls could be seen taking photographs of the knives.

Pictures: PA. The suspect is led away in handcuffs after police wrestled him to the ground.

PA. A forensics officer recovers a knife from the scene.