The quick-thinking man who grabbed a 5-foot-long whale’s tusk from the wall of a historic London building to charge a terrorist on a stabbing rampage is an immigrant from Poland.

Identified only as “Lucasz,” by the Times of London, the man was working as a chef in the kitchen at Fishmongers Hall, an events venue and an eclectic museum with roots back to the 1600s.

The tusk, from a medium-sized whale called a narwhal, was among the fishing industry memorabilia that decorate the hall.

The terrorist, Usman Khan, 28, a jihadi paroled in December after serving half of a 16-year sentence for plotting to blow up a series of London landmarks, had been in the hall for the first part of a prison rehabilitation conference put on by a Cambridge University.

Khan burst through the building’s doors wearing what appeared to be a suicide vest, threatening to blow the building up.

Witnesses said Lucasz grabbed the tusk off the wall and ran toward Khan, who held large kitchen knives in both hands. The convicted terrorist took off, slashing at anyone in his path. By the time he made it outside the building, he had killed a man and a woman and seriously injured three others.

Lucasz also received minor injuries from the knives, but nevertheless chased the terrorist outside, using the tusk as a spear. He was joined by another man, believed to be a conference participant, who sprayed a fire extinguisher at Khan as he ran to the nearby London Bridge.

Thomas Gray and Stevie Hurst, tour guides with a company called Small Cars Big City, were driving over the bridge to pick up clients. They jumped from their cars and ran to help when they saw Lucasz and two other men pinning the knifeman down on the ground.

“I saw that he had two kitchen knives with blades about 8 inches long,” Gray told the Daily Mail. “One in each hand. One of the knives appeared to be attached to his hand by duct tape.”

Gray stomped on Khan’s hand, forcing him to drop one of the knives. Hurst kicked him in the head for good measure.

Another man, an undercover, off-duty transit cop who was walking on the other side of the bridge, ran through traffic, jumped the divider and grabbed one of the knives.

The heroes rolled Khan over and saw the vest, which turned out to be fake, as police moved in. The cops shouted warnings for the heroic citizens to get back, yelling that Khan had a gun in his bag.

Whether or not he did, or whether the police were just trying to get us to move away, I don’t know,” Gray said. “I saw the police shoot him three or four times and then heard a dull thud.”