In one of the many extraordinary acts of bravery on Friday, a young man driving his car across London Bridge pulled over to help a group of civilians bring down a convicted terrorist who had already killed two people and injured three others.

Thomas Gray, 24, a tour firm manager, stopped his classic Mini Cooper with his colleague Stevie in the front passenger seat, and ran towards a group of “five or six other blokes” as the attacker, named as Usman Khan who was only released from prison 12 months ago, was wrestled to the ground.

As he ran towards the scene without hesitation, he heard a policeman yell out: “He has got a bomb”.

“One thought was going through my mind – stop the dude. I’ve played rugby for most my life and the rule on and off the pitch is ‘one in, all in’.

“I did what any Londoner would do and tried to put a stop to it,” a shaken Mr Gray told the PA news agency afterwards.

“He had two knives on him, one in each hand, and it looked like they were taped to his hands,” Mr Gray said.

“I stamped on his left wrist while someone else smacked his hand on the ground and kicked one of the knives away.

“I went to pick up the knife when I heard a cop say ‘he has got a bomb’.

“I then got back and hid behind a school bus which was full of kids at the time.”

Mr Gray, who remained at the scene as London was locked down for five hours, said he saw “two or three” shots fired by police hit Khan, who then “hit the deck”.

“I then heard a fourth one and then a pop and a bang, followed by ‘run, run, run’,” he said.

“I turned and ran and then heard a volley of shots from behind us.”

Heroic passerby 'stamped on wrist' of London Bridge terrorist to stop him taking more liveshttps://t.co/px8zCqBAMp pic.twitter.com/EpXYpr44I5

— ITV News (@itvnews) November 29, 2019

Mr Gray told ITV News the attacker was being chased by five men with a “fire extinguisher” before he was wrestled to the ground.

“So Stevie and I just thought what to do and just kind of ran towards it, left the cars where they were, and then tried to do our best to apprehend the suspect.”

“I wouldn’t say I kicked the knife, I kind of stamped on his wrist as hard as I could.

Clearly shaken after the horrific event unfolded, he said the “police armed response were really, really quick, got there almost instantaneously.”

“We saw the guy get shot a couple of times and then hit the deck.”

Thinking more of the safety of other, Mr Gray told ITV he protected “a school bus full of little children and made sure that the girls at the back were OK”.

George Robarts, a translator who was on the bridge at the time, said another unidentified man wearing a suit and overcoat had run through traffic and jumped the central partition to tackle the attacker with several people.

“We ran away but looks like he disarmed him,” he said in a tweet. “Amazing bravery.”

Other Twitter users praised the man seen removing the knife. One said he should have his mortgage waived and another said he should never have to buy a drink again.

The attacker, who was wearing a fake suicide vest and has not been named, was killed by police on London Bridge in full view of horrified onlookers.

As questions were being asked as to how a convicted terrorist was allowed to walk free on the streets of London, the Metropolitan Police Commissioner Cressida Dick told reporters the investigation was “very fast moving and dynamic”, with officers working to identify the attacker and his motive.

-with AAP