Members of the public used a “narwhal tusk” and a fire extinguisher to try to restrain the London Bridge attacker, according to witness reports.

Video footage shows bystanders overwhelming the knife-wielding terrorist on the ground, with police pulling a man in jeans off the suspect right before opening fire.

In other footage, someone is seen spraying the attacker with a fire extinguisher, while someone else hits him with a large white pole, reportedly a narwhal horn he grabbed off the wall at Fishmongers' Hall, a witness said on Twitter.

The man, a Polish chef at the hall, ran towards the terrorist with the sea creature’s tusk after the terrorist threatened to set off an explosive, according to The Times.

As police start taking over, a man in a suit can also be seen backing away with a knife in his hand.

Witness Thomas Gray said the attacker had been “wrestled” to the ground by “five or six other blokes” when he reached him. He said he got out of his car after seeing people running on the bridge.

Mr Gray said he “stamped on his left wrist” to try and release one of the man’s two knives “while someone else smacked his head on the ground and kicked one of the knives away”.

“I did what any Londoner would do and tried to put a stop to it,” Mr Gray said.

A man and a women were killed in a stabbing spree by 28-year-old Usman Khan, a convicted terrorist named by police, and several others were wounded after the attack at around 2pm on Friday.

Police fatally shot Khan, who was wearing a fake suicide vest, at the scene.

Narwhal tusks, which an onlooker reportedly hit the terrorist with, sell for several thousand pounds and were once highly sought-after objects by Europeans, who considered the animal a "sea unicorn". Queen Elizabeth I is said to have spent £10,000 on a narwhal horn, roughly around £1.5m today.

The Times reported the attacker was attending a Cambridge University conference on prisoner rehabilitation at Fishmongers’ Hall, at the north end of the bridge, and had threatened to blow up the building.

One witness said he spoke to one of the men who helped wrestle the knifeman to the ground after the incident who told him “he was in prison with the attacker”.

The Archbishop of Canterbury called the members of the public who tackled the attacker "astonishingly brave" and London mayor Sadiq Khan calling them "the best of us".

Boris Johnson praised the "extraordinary bravery" of onlookers who intervened, as well as praising emergency service workers.