This is the dramatic moment a have-a-go hero tackles a machete wielding robber after a smash-and-grab raid on a luxury City jewellers.

The smartly dressed City worker leaps on the back of the raider in the middle of a crowded street in front of lunchtime shoppers yesterday.

The brave man struggles with the raider who then pulls the two foot long machete from his trousers and wields it menacingly over his head.

The extraordinary drama unfolded outside the exclusive Carr Watches and Diamonds store in Liverpool Street at 2.30pm yesterday.

Dramatic footage taken by a passer-by on a camera phone also shows a police officer in plain clothes drive his unmarked car at the scooter raiders in an attempt to block their escape.

The unarmed City of London police officer - who was on duty and passing the scene by chance - also chases after the man but is forced to retreat after he too is threatened with the machete.

The suspect, clad in black and wearing a motorcycle helmet, had been abandoned by his two accomplices who sped away on two mopeds when police arrived.

He was later traced by armed police to a nearby underground car park where he was arrested. The other two suspects remain on the run today.

Eyewitnesses described how the three raiders struck at the luxury jewellery store shortly after 2.30pm when many City workers were on the street returning from lunch breaks.

Three employees at the jewellers, which sells high-end pieces by Rolex, Franck Muller and Audemars Piguet for as much as £50,000, watched terrified from their desks as the gang fled in “a matter of seconds”.

The gang used a concrete slab to shatter the toughened glass door before smashing open glass cases using sledgehammers to steal watches worth thousands of pounds.

Staff at Carr jewellers today paid tribute to the have-a-go hero - who the Standard is not naming - who tried to tackle the robbers.

Ish Ahmet, 30, was working when the gang stormed in and started to grab luxury goods.

He said: “It was all a shock, it was over so quickly. The City worker chased after them, it was pure instinct. He tried to grab one.

“It was a brave thing to do. He was tough and is back at work today, he is OK. They came in the shop and then it was a bit of a blur obviously it was a shock for us.”

The shop was re-opening today and Mr Ahmet added: “We are not sure what they got away with, some watches we think maybe Rolexes but we are not sure at the moment. I have been through this other times at other jewellery stores in London where I have worked. You just have to get back on with it.”

An eyewitness who works nearby said: “I could not believe what I was seeing in the middle of Liverpool Street. I heard a crash and looked and there was a guy swinging a sledgehammer.

“It was surreal like something out of a Hollywood movie. The next thing a smartly dressed man tried to tackle one of the robbers but was then threatened with a massive machete. We were all looking on in total shock and horror, it did not last long but everything was total chaos.

“The man who tried to stop them was a real have a go hero. He could have been killed. He looked tough but when you are against a machete you have no chance. At least he slowed them down though.”

Another witness said : “It was crazy, like Grand Theft Auto. It all happened so fast.

“Suddenly the gang were smashing through the window with a huge brick and then smashing a glass box inside the shop with a sledgehammer.

“The men grabbed some jewellery and two of them got on a Vespa each and sped off but one had been left behind. “

David Williams, 47, who runs a key cutting shop opposite the crime scene said: “I heard a big crash but at first thought it was from the construction site next door. Robbers have hit another jewellers on this street but this was something else.

"It was very brazen to raid a store in the daytime. I guess they thought they could get away easily by wending their way through the narrow City streets. It has been a shock for us all down here.”

Police arrested the robbery suspect in an underground car park 300 metres away in Gravel Lane.

A City of London Police spokesman said: “Police called at 2.34pm to reports of a smash and grab in progress at a jewellers in Liverpool Street.

“Officers attended to find three men on two mopeds outside the jewellers.

“An officer at the scene was threatened with a machete when he confronted the group.

“Officers followed the suspects to a car park in Gravel Lane where one was arrested. The machete has also been recovered. Armed officers also attended.

“The group used sledgehammers to smash windows of the jewellers. A sledgehammer has been recovered. There are no reports of any injuries at this time. Two men remain outstanding.”