UPDATE: This new image of the gun being examined by forensic police officers has been tweeted by LBC Radio.
An armed man has been detained by police in a busy London high street.
Police raced to a Barclay's bank on Borough High Street, near London Bridge, on Thursday afternoon.
Eyewitnesses reported a man wielding what looked like an AK-47.
ITV Journalist Darren Burn, who was at the scene, tweeted a picture apparently showing the suspect being detained.
Now where the suspect has been detained by Guy's hospital. He's in the blue T-shirt. pic.twitter.com/iYJOQyxZHr— Darren Burn (@dazburn) July 25, 2013
A Met Police spokeswoman said officers had been called at about 1.47pm on Thursday to reports of an armed robbery on a bank in London SE1.
"A man was arrested, and was taken to South London police station," she said.
"The incident is being dealt with by the Met's flying squad.
"We believe a firearm was involved but not used."