Painting took two years to restore and was returned to gallery in July

Shannon was jailed for six years and banned from all Irish art galleries

He then 'collapsed' onto the artwork - but witness said he used his fist

Court heard he calmly walked into Irish National Gallery in Dublin in 2012

A man who punched a hole through an £8million Claude Monet painting has been jailed for six years and banned from all galleries - despite claiming he collapsed onto it due to a heart condition.

Andrew Shannon strolled calmly into the National Gallery of Ireland in Dublin before attacking the 1874 work Argenteuil Basin with a Single Sail Boat, which was left needing two years of repairs.

The 49-year-old, who later underwent a quadruple heart bypass, denied deliberately tearing the painting and told police he had felt dizzy and lost his balance.

Destroyed: Andrew Shannon, 49, left a huge hole in Monet's Argenteuil Basin with a Single Sail Boat (1874)

Evidence: The jury saw CCTV which showed Shannon raising his arm just before the painting was ruined

But a witness told Dublin Circuit Criminal Court his movement was a 'lunge' and Shannon's fist had gone straight through the painting like a 'hammer'.

And the court heard Shannon had 48 previous convictions, including for handling stolen maps worth £5,000 which dated to 1651.

A jury of seven woman and five men was told how Shannon walked into the gallery just before 11am on June 29, 2012.

He walked over to the Monet painting to look at it before disappearing, coming back and launching the attack - which was captured on CCTV.

Instead of his clenched hand falling low on the painting, it made contact above his eyeline - meaning he would have had to raise his arm, the court heard.

Security staff and two horrified tourists from New Zealand helped call an ambulance after Shannon told them he had unstable angina.

Jailed: Shannon (pictured) told police he had unstable angina and later underwent a quadruple heart bypass - but a jury found him guilty of damaging the painting after an eight-day trial at Dublin Circuit Criminal Court

He was treated by a paramedic who administered a glyceryl trinitrate spray and aspirin.

Despite the medical crew finding he was in a safe condition, he was taken to hospital where he was released the same day and interviewed by police.

During the interview he told officers he had a heart condition and had done nothing wrong.

But tourist Michael Williams told the eight-day trial he had seen a man with a clenched fist put it straight into the Monet.

He said he grabbed the man, who said something like he felt faint, and moved him into the middle of the room to get him away from the paintings.

Mr Williams' wife Toni Ashton added she was standing beside her husband when she saw an arm appear and a fist go through the Monet.

She said it was like a 'hammer' and described the movement as a lunge.

Restored: The painting has since been returned to its original state - but many fragments were lost forever

Good as new: Experts point out the meticulous work on the painting, likened to microscopic needlework

Police also found a tin of paint stripper in Mr Shannon’s bag - but the judge later concluded it was for his job as a French polisher.

Consultant surgeon Nicholas Walcot told the court that in July 2013, after he had been in prison for almost a year, Mr Shannon underwent a quadruple heart bypass because he had a 90 per cent blockage in three vessels of the heart.

But the surgeon said he would expect only one in 100 people with the condition to have dizzy spells, and if he fell down he would normally have remained unconscious rather than getting up.

Judge Martin Nolan, who directed the jury to find Shannon not guilty of damaging two more paintings at Dublin's Shelbourne hotel, said the 49-year-old must have known the painting was valuable.

He added it was a 'peculiar crime' and it was 'abnormal' for Shannon to cause as much damage as he did.

He sentenced him to six years' jail and suspended the final 15 months on strict conditions - including that Shannon not enter into a public painting gallery or any other building where paintings are publicly displayed.

The maximum sentence for the offence, to which Shannon pleaded not guilty, was ten years.

Masterpiece: Painted in 1874 when Monet was working from a boat on the Seine, Argenteuil Basin with a Single Sail Boat is the only work by the renowned Impressionist which is in the Irish national art collection

A previous jury in the case had been discharged last December after failing to reach a verdict.

The artwork was ripped apart in a devastating three-branch tear and was finally restored this year following a painstaking 18-month restoration.

Laid end to end, the tears would have been about a foot long in an artwork less than four feet square.

Conservationists removed the painting from its frame and delicately sewed together thousands of fine threads which made up the canvas.

Seven per cent of the pieces of the Monet - the only work by the artist in Ireland's national collection - could not be saved, some splitting into powdery dust.

Sean Rainbird, director of the National Gallery of Ireland, likened the meticulous repair to microscopic needlework.

'It was huge damage, shocking damage,' he said.

'This project to restore and conserve one of the gallery's most popular impressionist works of art is testament to the outstanding expertise and dedication of our professional team of conservators.'