A moped gang armed with hammers raided a luxury jeweller in broad daylight as bystanders filmed on mobile phones.
Dramatic footage showed six robbers dressed in black and wearing helmets speeding away from Boodles in west London as smoke poured from the shop.
The gang stormed into the Basil Street store in Knightsbridge and smashed through glass displays with hammers just after 10.35am on Wednesday.
They stole jewellery but no one was hurt, said police.
Video filmed from a neighbouring building showed the six robbers, one wielding a large sledgehammer, driving off on three mopeds as shocked passers-by watched on.
"One scooter mounted the pavement they were waving sticks and shouting at people. It was terrifying," a witness told the London Evening Standard.
"There is so much security around here they were taking a big risk."
A Boodles spokeswoman said: "I can confirm that there was unfortunately a robbery at Boodles Knightsbridge showroom this morning. I can also confirm that nobody has been hurt.
"The police are handling the situation and Boodles is unable to comment any further."
The smoke seen billowing from the shop is thought to have been generated by a security alarm.
A Metropolitan Police spokesman said the force was called to reports of a robbery at 10.37am.
He added: "A number of suspects had arrived on motorscooters, entered the store and then used hammers to smash their way through counter displays.
"The robbers removed property from the displays and then made off on the bikes."
No one has been arrested and an investigation is underway, police said.
The capital has been gripped by a moped crime wave in recent months, prompting calls from some for police to be given stronger powers to tackle offenders.
