Brexit campaigners have relied on the trope of the “Polish plumber” coming to work across the English Channel to rally support to leave the European Union.

But Saturday, Poles and other immigrants in Britain were being lauded as a crucial part of English society after a Polish man grabbed a decorative narwhal tusk from Fishmongers’ Hall and rushed to help stop the London Bridge attacker who fatally stabbed two people before being shot dead by police.

As one tweet put it: “Some people in the UK: We don’t need foreigners living in our country. Lukasz, the Polish chef who tackled the killer on London Bridge: Pass me my five foot Narwhal tusk!”

Authorities have not formally named the man, but British media has identified him by the first name Luckasz. Polish speakers, however, have pointed out that his name is more likely spelled Lukasz.

Speaking on Saturday, London Mayor Sadiq Khan praised the man’s heroism and confirmed he is of Polish origin.

“One of the great things about London is its diversity, so I’m not surprised at all,” said Khan. “When I say ‘the best of us,’ I include E.U. citizens as well.”

Others on social media seconded the sentiment. “If a Polish chef attacking a terrorist with a whale horn can’t unite our country I don’t know what can,” one user wrote on Twitter.

The attack took place Friday near Fishmonger’s Hall, a historic building now used as an events space. The Polish man reportedly worked in the service industry there, according to news reports. When the attack began, he grabbed the closest thing he could find to arm himself: a five-foot narwhal tusk.

The British newspaper the Times interviewed the man’s colleague who said he was “cut in the hand but not in critical condition.”

“Being stabbed didn’t stop him giving him [the attacker] a beating,” the colleague said. “Luckasz is a hero.”

Queen Elizabeth II also praised the bravery of the Polish man and another bystander who intervened with a fire extinguisher.

“I express my enduring thanks to the police and emergency services, as well as the brave individuals who put their own lives at risk to selflessly help and protect others,” she said.