A PC has been hailed a hero after chasing a teenager who aimed a replica handgun at him and pulled the trigger.

Brent undercover cop PC Ben Reidy watched the youth cock the imitation firearm on the South Kilburn Estate and heard the crack as the hammer hit the metal of the empty chamber.

The weapon was so convincing it even fooled firearms officers who arrived after the incident, in October, but he carried on the chase until the boy, thought to be 18, had been caught.

PC Reidy and colleague PC Jason Tsang, who was also threatened with the gun, have been held up as part of the Met police Heroes Week and praised by Mayor of London Boris Johnson.

Describing the chase, PC Reidy said: “He stopped and then turned round, I stopped as well because I didn't want to jump on him. That's when I saw the gun.

“He cocked it, the gun was in between his legs, he lifted it up pointed it towards me and it looked like he pulled the trigger.

“I heard a cracking noise, I thought he had taken a shot at me. He turned round and started running, I ran after him.”

He added: “I thought I might get shot. I didn't actually think I could get killed. It wasn't until afterwards that I thought what could have happened.”

The two officers had stopped the youth after seeing him on his bike but he tried to ride around their squad car, and then ran away.

PC Tsang followed him on foot but dived for cover after the teenager aimed the gun at him.

PC Reidy jumped out of the car and carried on the chase before being confronted by the replica.

The teenager was arrested after back up arrived but claimed he knew the gun was fake and was jailed for three years for two counts of possessing an imitation firearm with intent to cause fear or violence.

The officers are on the plain clothes Borough Tasking Unit, which covers the whole of Brent.

The Met's Acting Commissioner Tim Godwin said: “These officers have showcased the Met's commitment to being there for London by tackling extremely challenging scenarios head on.

“They are extraordinarily brave and I am heartened to see that they will be recognised for the work they have done. We are immensely proud of them.”

Mr Johnson said: "I have the utmost respect and admiration for the brave men and women who put their lives on the line every day to make this city a safer place for us all.”