He is not, however, as irreplaceable as some people appear to believe.
Among the items he had deposited was an irreplaceable £5,000 IWC GST Aquatimer watch he bought to give to his nine-year-old son on his 18th.
In a statement, the group added: "What has been lost are the irreplaceable collections of reference and lending non-fiction books, covering every conceivable subject, giving that extraordinary breadth and depth of subject coverage that only long established libraries can provide.
Sardet's book, called Plankton, merges science with art and illustrates what he calls "the irreplaceable beauty and diversity of planktonic life forms", but it comes with a warning that the world's oceans are being changed by climate change and acidification.
Agricultural research institutions have been closed or privatised and the agricultural advisory service dismantled, leading to the loss of an irreplaceable knowledge bank and the decline of agriculture.
Ailing he may be, but Mr Arafat has revamped himself as the irreplaceable glue that holds what remains of the Palestinian regime together.Palestinian reformers say he can get away with such obstructiveness because of America's policy towards him.
Unlike many of his breed, Mr Welch didn't prove irreplaceable, though.
Footballers with the ability to change the course of games singlehandedly tend to be irreplaceable.
By these standards, the sheikh's was reckoned to be a relatively pragmatic voice.Israeli leaders, intent on crushing Hamas before Israel's possible withdrawal from Gaza, have suggested that the sheikh, the "mastermind of Palestinian terror", enjoyed an irreplaceable position in the Islamist organisation.
Helium, prized for its unique combination of physically desirable qualities, is irreplaceable for many purposes.
Only Berlusconi thinks he's irreplaceable".Reportedly, Mr Berlusconi's main reason for respecting his new opponent was that he comes across well on television.
