This is the moment a masked thug wields a hammer as he and a fellow moped raider target terrified pedestrians in the heart of London.

The men, joined by another pair of raiders armed with a crowbar, roared around the West End on two scooters and carried out at least one theft.

Evening Standard photographer Alex Lentati was almost knocked down by one of the bikes when it mounted the pavement outside the BBC’s HQ, Broadcasting House.

Other witnesses described how the pillion passengers waved their weapons to ward off any have-a-go heroes.

The four “brazen” thieves were photographed at about 2pm on Thursday as they targeted pedestrians in Langham Street, yards from the entrance to the BBC Radio 1 studio.

Scotland Yard said officers were investigating one report of a theft of an iPhone from a woman in her forties on Great Portland Street just before 2pm.

Moped Gang wielding hammers - In pictures 6 show all Moped Gang wielding hammers - In pictures 1/6 Moped gang with hammers seen riding around near the BBC Broadcasting studios in a threating manner and trying to steal people mobile phones The Mega Agency 2/6 Moped gang with hammers seen riding around near the BBC Broadcasting studios in a threating manner and trying to steal people mobile phones The Mega Agency 3/6 Moped gang with hammers seen riding around near the BBC Broadcasting studios in a threating manner and trying to steal people mobile phones The Mega Agency 4/6 Moped gang with hammers seen riding around near the BBC Broadcasting studios in a threating manner and trying to steal people mobile phones The Mega Agency 5/6 Moped gang with hammers seen riding around near the BBC Broadcasting studios in a threating manner and trying to steal people mobile phones The Mega Agency 6/6 Moped gang with hammers seen riding around near the BBC Broadcasting studios in a threating manner and trying to steal people mobile phones The Mega Agency 1/6 Moped gang with hammers seen riding around near the BBC Broadcasting studios in a threating manner and trying to steal people mobile phones The Mega Agency 2/6 Moped gang with hammers seen riding around near the BBC Broadcasting studios in a threating manner and trying to steal people mobile phones The Mega Agency 3/6 Moped gang with hammers seen riding around near the BBC Broadcasting studios in a threating manner and trying to steal people mobile phones The Mega Agency 4/6 Moped gang with hammers seen riding around near the BBC Broadcasting studios in a threating manner and trying to steal people mobile phones The Mega Agency 5/6 Moped gang with hammers seen riding around near the BBC Broadcasting studios in a threating manner and trying to steal people mobile phones The Mega Agency 6/6 Moped gang with hammers seen riding around near the BBC Broadcasting studios in a threating manner and trying to steal people mobile phones The Mega Agency

Police said the pedestrian was about to cross the road when a moped drove towards her. The pillion passenger pushed her and snatched her phone from her hand. She was uninjured.

The incident is the latest in a crimewave involving criminals on mopeds carrying out robberies and snatches. Met figures show moped-enabled crime has risen seven-fold in two years, from 1,053 in 2014 to 7,668 last year.

Mr Lentati was walking on Langham Street when he “saw this motorbike come round the corner fast”.

He said: “At first I thought it was just bad driving, but then he mounted the pavement and started coming at me at fairly high speed. I’d just come off the phone and was putting it in my pocket.

"As the bike got closer it rode at me on the pavement, then whizzed past me on the inside next to the wall.

“The audacity of it was that another one turned up and then they went round the block and came back again tearing down Great Portland Street.

"When they came round the second time one of them brandished the hammer, like they didn’t want anyone to chase them or get close. It felt very brazen.”

BBC staff told the Standard that in recent months such incidents have become commonplace. Internal memos within the corporation have warned staff to be vigilant of the moped gangs.

Andrew Bomford, a reporter for BBC Radio 4, saw the two bikes “zoom” down Great Portland Street and try to snatch something from a man on a zebra crossing.

He said: “They almost clipped him as they were going past. He threw his hands up in the air and started running after them. They turned up the street towards the BBC.

"The guy that had been almost hit was chasing after them, and they came past me. Someone on the second bike was waving a hammer in his hand.

“It seemed to me like it was a warning to not try and follow them or grab them, or he would hit you. It’s completely brazen, and it’s happening all the time, and it’s the same thing each time.”

Police have drawn up a list of about 200 individuals who they suspect of the majority of moped-related crimes, but they are hard to prosecute because of the difficulty in securing evidence.

Many are not pursued because of fears for their safety and that of other road users and it is difficult to identify them when they are covering their faces.

Chief Superintendent Peter Ayling, head of policing in Westminster, said: “We are working hard to keep the public safe. We have been made aware of this serious incident and it is a top priority to identify and arrest these reckless offenders.”