A £30m Leonardo da Vinci painting has been stolen from a Scottish castle after two men joined a public tour and overpowered a guide.
A "substantial reward" has been offered for the painting's return
It is by no means the first theft of its kind.
Julian Radcliffe, chairman of the Art Loss Register told BBC Radio 4's Today programme that such a heist "would probably be easier to do it when it was open to the public rather than at night when all the alarms were set".
"If you're going to allow public access, particularly to a location of this sort, which is not in the centre of a major city, it is difficult to guard against this type of attack," he said.
He added that thieves had several options after they got away with such paintings, and either waited decades before trying to offload them, tried to ransom them or attempted to pass them off as high-quality copies.
BBC News Online looks at other famous raids - and recoveries - over the years.
Mona Lisa, Paris, 1911
The Louvre: The Mona Lisa now has its own room
It was called the biggest art heist in history - and Italian workman Vincenzo Peruggia's theft made Leonardo da Vinci's portrait the most famous painting in the world.
Annoyed by how many Italian works were in the French collection, Peruggia took the Mona Lisa from the wall of the Louvre while he was alone in the room and walked out with it under his smock.
It was missing for two years - but the French public queued in their thousands to see the blank space on the wall and the Mona Lisa's fame was guaranteed.
National Gallery, London, 1961
Goya's portrait of the Duke of Wellington was in the news after the UK government frantically assembled enough money to stop it being bought by a foreign collector.
But its high profile made it an attractive target and an unemployed driver, Kempton Bunton, admitted going into the National Gallery through an open window and going out with the painting under his arm.
He said he wanted to use the ransom money to buy TV licences for the poor and he served three months in jail. But papers released by the National Gallery in 1996 revealed that he was probably innocent.
Russborough House, Ireland, 1975-2002
Possibly the most burgled property in art history, a total of 45 paintings have been taken from this stately home in four raids between 1975 and 2002.
Two paintings taken from the building last year had previously been stolen in 1986 and returned seven years later.
The 2002 raid took place just days after two paintings taken from a past raid were recovered.
Boston, US, 1990
The biggest heist in US history, the $300m haul taken from the Isabella Stewart Gardner Museum - including works by Vermeer, Rembrandt and Manet - is still missing.
The paintings were taken when two men in police uniforms turned up at the museum in the early hours, claiming to be responding to a disturbance in the grounds - but handcuffed the security guards to railings as soon as they were let in.
A $5m reward still awaits the person that finds the loot.
Amsterdam's Van Gogh Museum had one of the more unsuccessful thefts
Two masked armed men took 20 paintings - worth at least $10m each at the time - from Amsterdam's Van Gogh Museum.
Police said at least one of them may have hidden in the museum on Saturday afternoon, overpowering two guards in the early hours of Sunday and forcing them to turn the alarms off.
But the paintings were found in the getaway car less than an hour after they escaped - and nobody quite knew why.
The Scream, Oslo, 1994
While most of Norway was watching the opening of the Winter Olympics in Lillehammer, two thieves broke into a gallery in nearby Oslo and took Edward Munch's most famous work.
They set off an alarm - which was ignored by the guard, and the thieves left a note reading: "Thanks for the poor security."
A long investigation eventually recovered the masterpiece after a piece of the frame was left at a deserted bus stop.
Stockholm, Sweden, 2000
In one of the most audacious thefts, three masked armed robbers walked into Stockholm's National Museum as visitors were milling about, took a Rembrandt and two Renoir paintings and ran out again.
They escaped from the waterfront gallery by motorboat - but police stumbled upon one of the paintings during a drug investigation four months later.
Eight men were sentenced to up to six and a half years each in jail as a result.
Asuncion, Paraguay, 2002
Police said the 80-foot tunnel may have taken two months to dig - it began under a shop and led into the National Fine Arts museum in Asuncion, which was hosting the most valuable exhibition in its history.
A gang using false names had rented the shop and carried out the heist at night, taking £500,000 worth of art.
Manchester, UK, 2003
This Van Gogh painting was among those stolen in Manchester
Three paintings by Van Gogh, Picasso and Gauguin worth £4m were stolen from the Whitworth Gallery in Manchester after thieves evaded CCTV cameras, alarms and 24-hour rolling patrols.
But they were found the next day, slightly damaged and crammed into a tube behind a public toilet.
A note was attached to the paintings claiming the motive of the thieves was to highlight poor security at the gallery.