A man has been jailed for two years for defacing a painting by artist Mark Rothko.
Wlodzimierz Umaniec, 26, also known as Vladimir Umanets, defaced the mural, worth in the region of £5 million to £9 million, at London's Tate Modern gallery on 7 October this year.
Umaniec, a Polish national living in Worthing, West Sussex, admitted criminal damage to the value of in excess of £5,000 - but estimates suggest the restoration of the painting will cost around £200,000.
The Rothko was defaced with words: :"Vladimir Umanets, A Potential Piece of Yellowism."
Judge Roger Chapple, at Inner London Crown Court, told Umaniec: "Your actions on the 7th of October of this year were entirely deliberate, planned and intentional."
The vandal, who co-founded the artistic movement "yellowism", stepped over a barrier in the art gallery and daubed his name and the words "12 a potential piece of yellowism" before fleeing.
The court heard that he went to the gallery intending to put his "signature" on a picture, but decided to damage the Rothko painting only at the time he saw it on display.
The gallery was then put into "operation shutdown" with people prevented from leaving or entering the building.
Speaking about "yellowism", Judge Chapple said it was "wholly and utterly unacceptable to promote it by damaging a work of art" which he called a "gift to the nation".
He said it was "abundantly clear" that Umaniec was "plainly an intelligent man" and told the court he had described Rothko as a "great painter" in a letter he had written to him.
The judge also said the incident had led to galleries reviewing security arrangements at a cost to themselves and the taxpayer.
"The effects of such security reviews is to distance the public from the works of art they come to enjoy," he said.
Gregor McKinley, prosecuting, said: "Sotheby's has given Tate Modern a verbal estimate of pre-damage value of approximately between £5 million to just over £9 million."
He added: "The work required to restore this picture will be complex and lengthy.
"Complications to this work include the unique painting technique used by the artist and the fact the ink used by Mr Umaniec has permeated the paint layers and the canvas itself."
Mr McKinley said work to restore the painting will take about 20 months and cost "something around £200,000".
Gareth Morgan, defending, said it would take a "significant amount of effort, expert effort at that" to restore the "important, valuable piece of art".
Paintings by Russian-born artist Rothko often fetch tens of millions of pounds.
Earlier this year, his Orange, Red, Yellow sold for £53.8 million - the highest price paid for a piece of post-War art at auction.
The 1961 painting went under the hammer at Christie's in New York.
The defaced painting, called Black On Maroon, was donated to the Tate in 1969 by Rothko himself.
Outside court before the sentencing, Ben Smith, who called himself a "yellowist", attempted to explain the concept: "Everything is equal. Everything is art. Everything is a potential piece of yellowism."
After the sentencing, Mr Smith, who had come along to support Umaniec in court, said Umaniec's time in prison would be "one of the most creative points for him" and will "give him a greater understanding of humanity".
Speaking about the incident he said: "This was not an act of destruction. It was an act of creativity.
"Now yellowism is a global phenomenon."
Art vandalism: from the Mona Lisa to Banksy
The world's most famous painting has been the subject of numerous thefts and attacks. It went missing for two whole years in 1911 when Louvre employee Vincenzo Peruggia stole it, trying to return it to Italy. 1956 was a bad year for Mona. Not only was it doused in acid but later that year a young Bolivian named Ugo Ungaza Villegas threw a rock at it, chipping some of the paint off. This incident prompted the decision to house the painting in bullet-proof glass.
In 2012, a well-meaning but artistically incompetent pensioner decided to attempt a restoration of Ecce Homo (Behold the Man) by Elias Garcia Martinez, a highly-prized 100-year-old fresco of Christ. It didn't work.
The very nature of Banksy's work means that his pieces are often at the mercy of vandals although he seems to suffer more at the hands of over-zealous councils and builders. His Parachuting Rat (pictured) piece fell foul of an Australian building firm who decided to drill a hole through it to install a bathroom pipe.
Rembrandt's The Night Watch, was attacked with a bread knife by an unemployed teacher named Wilhelmus de Rijk, in 1975.
Diego Velázquez's The Rokeby Venus was attacked with a meat cleaver by militant suffragette Mary Richardson. This black and white picture clearly shows the damage. Richardson was jailed for six months.
Quite why The Little Mermaid causes such outrage is beyond us but the statue has been defaced many times since it was placed in Copenhagen harbour in 1964. Edvard Eriksen's mermaid has been decapitated twice (once by Jorgen Nash and the Situationist Internationale), had her left arm sawed off and had holes blasted in her wrists and knees. Painful.
The Fall of the Damned by Peter Paul Rubens is a monumental piece of art measuring more than two metres square. In 1959 a vandal threw acid on it. According to the culprit, he did not directly destroy the work, claiming the acid "relieves one from the work of destruction", whatever that means.
Danaë, by Rembrandt, was attacked in 1985 by a clinically insane gentleman who threw sulfuric acid on the canvas and cut it twice with his knife, causing horrific damage. The entire central part of the painting was destroyed but extensive restoration managed to salvage it.
In 1845 a rather intoxicated William Lloyd took issue with this vase and threw another sculpture on top of it, smashing it to pieces. Lloyd was jailed for two months.
With a cricket bat concealed in his trousers, Paul Kelleher sneaked into London's Guildhall Art Gallery and decapitated the Iron Lady. After waiting for police to arrest them he said simply: "I think it looks better like that."
Pablo Picasso's famous ant-war masterpiece Guernica came a cropper in 1974 when a vandal spray-painted it with the slogan 'Kill Lies All'. PA
Damien Hirst's lamb in formaldehyde, Away from the Flock, wasn't safe from vandalism despite being in a glass case. Mark Bridger poured black ink into the tank in 1994 whilst it was on display at the Serpentine Gallery. PA