Moped thugs snatched gold necklaces from the throats of two women during a violent knifepoint attack in south London.
Horrifying footage shows a man wearing a helmet and clad in black leather leap from the back of a moped and lunge at the victims while brandishing the blade.
Two men appear to fight off the attackers using shopping bags during the incident in Bensham Manor Road, Thornton Heath, on Wednesday afternoon.
A second armed man leaps from the scooter and holds back one of the men while his accomplice rips the necklaces from the women.
Following the robbery, the gang appear to speed off towards White Horse Road leaving the terrified victims cowering behind a brick wall.
Police said one of the men who intervened, aged in his 70s, was injured as he was hurled to the ground during the attack.
He was taken to hospital for minor head injuries, a spokesman added.
Neighbours descried the robbery as “shocking” but “sadly not unusual”.
One woman, who lives in Bensham Manor Road and asked not to be named, told of the moment her husband rushed away from the aftermath of the scene.
She told the Standard: “My husband came rushing in and said there had been a commotion before an ambulance arrived and a man was wheeled out of the house opposite with bandages round his head.
“It’s shocking but it’s not unusual for round here. There have been a lot of muggings recently, and a lot of young men getting stabbed. It’s scary.”
A spokesman for Scotland Yard said a manhunt had been launched to find the suspects who were described as three white men and one black man.
He added: “Detectives in Croydon are appealing for information and witnesses after two women were robbed at knife-point of their gold necklaces in Thornton Heath.
“The women were approached by four men riding on two mopeds in Bensham Manor Road, on Wednesday, 20 September at around 3.10pm.