Two climate change protesters glued themselves to the frame of a John Constable painting, The Hay Wain, and attached their own image of an "apocalyptic vision of the future".
The alternative vision of the rural Suffolk farm featured an old car dumped in front of the mill, two aeroplanes and a washing machine in the back of the cart.
The Just Stop Oil (JSO) protesters targeted the National Gallery in London on Monday afternoon, forcing the evacuation of visitors, including a class of 11-year-old schoolchildren, from the room where the painting hangs.
JSO identified them as music student Eben Lazarus, 22, and psychology student Hannah Hunt, 23, both from Brighton.
They called for an end to new oil and gas licences in the North Sea.
Wearing matching branded t-shirts, the two campaigners crossed a rope barrier and attached the alternative printed image over the top of the painting.
They then each attached one hand to the picture frame and crouched below, loudly voicing their concerns about the climate, before security staff cleared the room.
Mr Lazarus, who described himself himself as an art lover, said: "Art is important. It should be held for future generations to see, but when there is no food what use is art?
"When there is no water, what use is art? When billions of people are in pain and suffering, what use then is art?"
The Hay Wain, which was painted in 1821, is one of the most popular paintings at the gallery and shows a rural Suffolk scene of a wagon returning to the fields across a shallow ford for another load.
Lazarus said: "We have stuck a reimagined version of the Hay Wain that demonstrates our road to disaster."
Hunt later said "the disruption will end when the UK government makes a meaningful statement that it will end new oil and gas licences".
She added: "I'm here because our government plans to license 40 new UK oil and gas projects in the next few years.
"This makes them complicit in pushing the world towards an unliveable climate and in the death of billions of people in the coming decades.
"You can forget our 'green and pleasant land' when further oil extraction will lead to widespread crop failures which means we will be fighting for food. Ultimately, new fossil fuels are a death project by our government.
"So yes, there is glue on the frame of this painting but there is blood on the hands of our government."
A spokesman for the National Gallery said the conservation team identified minor damage to the frame and disruption to the surface of the varnish on the painting, both of which have now been repaired.
A Metropolitan Police spokesman said: "At approximately 14.25 on Monday officers were called to a protest taking place inside the National Gallery involving two people."
It is the latest demonstration by the group which in the past week has allegedly targeted a Scottish art gallery and Sunday's British Grand Prix.
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