London, UK - Two climate activists have been found guilty of causing criminal damage to a Vincent Van Gogh painting's frame after gluing themselves to it at a London art gallery.

Just Stop Oil supporters Emily Brocklebank (23) and Louis McKechnie (22) had been accused of causing just under £2,000 ($2,375) of criminal damage to the frame, and they were found guilty during a trial heard on Tuesday.

Jonathan Bryan, prosecuting, said the activists used super glue to attach themselves to Van Gogh's 1889 work Peach Trees In Blossom at the Courtauld Gallery on the Strand on June 30.

But Francesca Cociani, defending the pair at Westminster Magistrates' Court on Tuesday, questioned Karen Serres, a curator at the gallery.

She said, "It's possible that this very painting has now increased in value because of the protest it was subject to by the defendants."

"Say the institute was to sell it on in 20 to 30 years, is it possible its value would now increase?"

Serres replied, "Absolutely not." The witness said she believes the painting cannot be sold.

CCTV footage showed the activists walking in the building at about 3:30 PM after purchasing tickets for an exhibition.

They then took off their jackets to reveal orange Just Stop Oil T-shirts and attached themselves to the artwork.

Bryan said, "They waited until the coast was clear, when the gallery attendants looked away or were perhaps distracted by another member of the group."

The prosecutor said, "These actions did in fact cause criminal damage."

He said the painting, which is worth "millions," was not damaged but the "valuable" frame was.

Bryan added. "The defendants say they were expressing their rights, under the European convention... to freedom of expression... and of assembly. They say the exercise of those rights gives them a lawful excuse. But these are qualified rights, not absolute rights."

Serres told the court it took three hours for the activists to be removed, with the incident lasting until after closing time. "There were concerns over how much of the glue had seeped into the frame and the painting itself," she said.

There were also worries about the solvent used by police to remove the activists, the court heard.

Serries said the frame, worth around £20,000 ($23,753), dates back to the 18th century.

"There were large areas of glue left behind and areas of solvent which had seeped into the gilding of the frame," she said. "Parts of the frame had fallen off."

Serres said it took six hours for the painting to be removed from the frame and put back again.

Brocklebank, a student, told the court, "When it comes to protesting, just speaking does not get a platform. By gluing, it gives a story which the media chooses to follow."

She added, "I didn't think I would cause much damage. Glue comes off."

The defendant said the painting's owner would have "consented" to the protest. She said, "Any good human would agree with trying to sustain life on Earth."

Brocklebank, from Leeds, who appeared in person, and McKechnie, from Devon, who appeared in custody from HMP Peterborough, denied intentionally damaging the frame. Brocklebank received a 21-day sentence, suspended for six months, and was given an electronically monitored six-week curfew. McKechnie was jailed for three weeks.

Xavier Gonzales-Trimmer (21) originally faced the same charges after being accused of "distracting the guards," but they were dropped. However, he was fined for failing to appear at the court for a first hearing.

The incident is one of many in recent weeks in which activists have attacked various famous paintings in galleries across England and Europe to draw attention to the climate and environmental crisis.

Another Vincent van Gogh, Sunflowers, was by was pelted with tomato soup at London's National Gallery in mid-October, as fellow activists from Just Stop Oil also glued themselves next to it.

Activists who targeted Johannes Vermeer’s Girl with a Pearl Earring in a Dutch museum last month were reportedly sentenced to two months in prison.

More have smeared cake on works by Leonardo da Vinci and thrown mashed potatoes at art by Claude Monet.

Almost all the paintings were covered by protective glass and largely undamaged.