LONDON.- When a London judge handed down prison sentences Friday to two climate activists, who threw soup on Vincent van Gogh’s “Sunflowers,” he said he wanted to deter protesters from trying similar stunts.

Judge Christopher Hehir sentenced Phoebe Plummer, 23, to two years in jail for damaging the painting’s frame during the 2022 attack at the National Gallery in London. Anna Holland, 22, received 20 months for the same offense. Their actions were “criminally idiotic” and could have caused “irreversible damage” to a masterpiece, Hehir said.

His words did not have the desired effect.

Just over an hour later, three other members of Plummer and Holland’s protest group, Just Stop Oil, entered the National Gallery’s “Van Gogh: Poets and Lovers” exhibition and threw Heinz vegetable soup over the painting again. They also splashed the orange liquid on another van Gogh “Sunflowers” painting, on loan from the Philadelphia Museum of Art for the gallery’s blockbuster show.

In a video of the incident, released on social media by Just Stop Oil, museum patrons appear startled. One person shouts: “Why are you doing that?” The London police said it had arrested the three activists.

A National Gallery spokesperson said in an emailed statement that “the paintings were removed from display and examined by a conservator and are unharmed.” The museum would “reopen the exhibition as soon as possible,” the statement added.

A spokesperson for the Philadelphia Museum of Art said that the National Gallery had informed the museum “that the painting has been cleaned and there is no permanent damage.”

Climate protesters have been grabbing media attention with stunts in museums since 2022, in a wave of actions that began in the Louvre in Paris and then spread to England, Germany, Italy and the United States.

Friday’s jail terms were the heaviest penalties handed down by a British court in response to such attacks. A protester who glued himself to the frame of another van Gogh work, “Peach Trees in Blossom,” at the Courtauld Gallery in London, was sentenced to a three-week prison term in 2022, but most activists have avoided jail time. Five Just Stop Oil members who stuck themselves to the frame around a copy of Leonardo da Vinci’s “The Last Supper” and spray-painted the phrase, “No new oil,” on a wall at the Royal Academy were each fined 486 pounds, about $650.

During Plummer and Holland’s sentencing hearing, Hehir said that acidic soup had a “corrosive effect” on the painting’s 17th-century wood frame and had lowered the frame’s value by an estimated 10,000 pounds, or about $13,000.

The judge said the duo’s action came close to damaging the masterpiece itself — within “the thickness of a pane of glass.” He added that “stupidity like this” could lead museums to withdraw cultural treasures from public view, or force them to introduce onerous security measures that would deter visitors.

During the hearing, Plummer, who uses they/them pronouns, read a lengthy speech in which they said that protest was a vital tool for raising awareness of climate change. Hehir interrupted repeatedly: “I’ve heard it before,” he said at one point. After Plummer said they were “a political prisoner,” Hehir interrupted to say, “We don’t have political prisoners in this country.”

Raj Chada, a lawyer representing Holland, told the court that the defendants had not intended to damage the painting and knew the museum had covered it with glass to protect it. Hehir dismissed that argument, saying the pair had blithely ignored the risks to van Gogh’s painting.

Plummer told the court that they expected a jail term and would accept the judgment “with a smile,” and as a member of the court staff led them away to start their sentence, they grinned. Then the pair hugged and blew kisses at their supporters in the courtroom.

This article originally appeared in The New York Times.