In the past (& fairly recently, in relation to any riots that ever take place there), people have suggested that it is lucky that the Parthenon Marbles (or Egyptian artefacts etc depending what is happening around the world) artefacts in the British Museum, otherwise they would have been more likely to be destroyed.
The assertions of this, assume that for some reason museums in the UK are completely secure – that accidents can’t happen & that every artefact remains forever in the same condition as it was when it was acquired.
Surely though, it would be something hard to own up to – and very galling to the original (& claiming to be rightful) owners, that their artefacts that you were “looking after safely” for them were lost or destroyed? It is hardly as though this is the first time  that such a story has surfaced.
Big News Network 
British artwork damaged at museums
Big News Network (UPI) Tuesday 6th November, 2012
LONDON — British officials said 199 art exhibits have been lost or stolen from Britain’s national galleries and museums during the last three years.
The figures, released under the Freedom of Information Act, revealed many of the artworks, including pieces by Poussin to Roy Lichtenstein, were damaged by the very staff members who are supposed to protect and preserve them, The Daily Telegraph reported Monday.
One of the incidents detailed in the Freedom of Information Act release revealed a James Francis Mauber portrait of 17th century poet John Dryden had an ornament knocked off its frame when a member of a tour group was knocked off balance by a security guard at the National Portrait Gallery.
Another incident involved a 17th century Edward East night clock at the British Museum being broken when a visitor tripped and a Japanese clock was damaged when a cleaner fell into it during a power outage.
The glass covering a photograph of Margaret Thatcher, taken by Helmut Newton, was cracked when a staff member fell as the frame was being lifted to be packed for loan and the artwork hit the ground.
“Britain’s museums and galleries are rightly renowned around the world for the quality of their collections and for their curatorial and conservation standards,” said a spokesman for the Department for Culture, Media and Sport.
“Inevitably, however, with so many items being transported, conserved, catalogued and displayed at any one time, a small number will from time to time get damaged,” the spokesman said. “We are confident though that the highest standards are maintained and that accidental damage to items is not a significant cause for concern.”