A 25-year-old man has been arrested on suspicion of robbery after a cash box was taken from a security guard at Natwest in Northumberland Heath.
Witnesses said a G4S van arrived at the bank in Bexley Road about 9.10am on Thursday and an employee of the security company had the case of money snatched from him.
A barber at Toks05 next door said he had just opened up the shop when the incident happened.
The worker, who was too frightened to be named, told News Shopper: "I saw a man sitting down outside the shop and he gave me a strange look.
"I thought he was waiting for a bus.
"When the security guard was about to go into the bank he just grabbed the case.
"This is the first time something like this has happened.
"I was so scared. Why did this happen this morning? We never experience things like this here."
The witness said the robber was white and slim and took off across Bexley Road down Northumberland Park.
Gary Whiffin, manager of Game Exchange, just a couple of doors down from the Natwest branch in Bexley Road, said: "An older gentleman came out of the bank and ran down Northumberland Park.
"He seemed like a customer who had been in there at the time.
"He was shouting "stop that guy".
"He sounded distressed when he was shouting which is why it caught the attention."
Mr Whiffin said a police car was on the scene "within a minute or so" followed by two more and an unmarked car as shoppers and shop workers milled around in disbelief.
The bank was closed for nearly three-and-a-half hours after the robbery, opening again at 12.30pm.
The suspect was arrested in Austen Road at about 12.45pm and witnesses have described forensics being at the scene.
A 32-year-old resident of the road said: "There was a massive police presence in the road and I saw forensics working looking for clues.
"I called the police because I saw the man acting suspiciously.
"They were at the scene within five minutes which was very impressive."
Not long after the robbery an ambulance travelling to an unrelated incident struggled to get down Bexley Road as it was blocked by police cars, the G4S van, a bus and a Tesco delivery van.
A Bexley Police spokesman added: "At this early stage it appears that a cash in transit security guard was robbed of a quantity of cash.
"No weapons were seen or used.
"A 25-year-old male was arrested a short while later at an address in Erith and remains in custody at an East London Police Station.
"The cash box has been recovered."
Anyone with information is asked to call Crimestoppers on 0800 555 111.
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