A Cartier ring worth £750,000 ($957,000) and a 12cm marble head are among the items that have previously gone missing from the British Museum.
The museum announced on Wednesday it was taking legal action against an unnamed staff member, who has been dismissed, and launched an independent review of security after items from its collection were found to be missing, stolen or damaged earlier this year.
The staff member has not been arrested.
We take a look at artefacts that have gone missing from the London museum over the years.
Gold jewellery and semi-precious gems
The items reported stolen on Wednesday included gold jewellery and gems of semi-precious stones, and glass dating from the 15th century BC to the 19th century AD, which were not recently on public display and were used mainly for research and academic work.
Museum director Hartwig Fischer said it had “tightened” its security arrangements, while chairman George Osborne said its priority was to recover the stolen items, find out if there was anything that could have been done to stop the theft and do whatever possible to prevent it from happening again.
In 2017, it was revealed a Cartier diamond ring from the museum’s heritage asset collection was missing.
It had been reported absent in 2011 but details of the loss were not made public at the time.
The absence was detailed six years later in accounts from the Department for Digital, Culture, Media and Sport, in which the jewellery was said to be worth £750,000.
“The museum takes the security of the collection extremely seriously," officials said at the time.
“The museum has since reviewed its security and collections management procedures and dedicated significant investment to improved security across the estate.”
Unusual museums around the world – in pictures
It was reported in 2004 that 15 Chinese artefacts were taken from the museum by a member of the public.
Described as “historically important”, the items reportedly included jewels, ornate hairpins and fingernail guards.
A Greek head
In 2002, the museum reviewed security after a 2,500-year-old Greek statue was stolen by a member of the public.
The institution said at the time that the Greek Archaic Gallery had been open to the public but there was no permanent guard on duty when the 12cm-high marble head was taken.
Curators and dealers across the world, along with Interpol, were alerted to look out for the head, which had a distinctive damaged nose and face.
Acquired by the museum in 1922, experts believed at the time that it could have been worth up to £25,000.
In 1993, Roman coins and jewellery worth £250,000 were stolen in a break-in through the roof of the museum.
Coins and medals
During the 1970s, the British Museum said a number of coins and medals were stolen.
Theft rises questions over safety of Elgin Marbles at British Museum
Itemising the stolen artefacts from the British Museum “could take weeks, if not months” and even calls into question the safety of the disputed Elgin Marbles held at the London institution, an expert in recovering stolen works of art has said.
The theft announced on Wednesday came amid one of the world’s most intractable cultural heritage disputes – the fate of the Elgin Marbles in the British Museum.
Greece has been campaigning for decades for the return of the sculptures, which once adorned the Parthenon on top of the Acropolis in Athens.
The country has long claimed they were illegally acquired during a period of foreign occupation, while British officials have rebuffed repeated demands for their return.
Christopher Marinello, a lawyer and expert in recovering stolen art, said the latest theft has exposed the museum to questions over the safety of the ancient sculptures.
“It makes one wonder whether the Parthenon Marbles are safe in the British Museum after all, and perhaps they should be returned to the museum in Athens for their security," he said.
“One of the arguments the British Museum has always given is they’re better preserved in the British Museum than they are in Athens."
He said the British Museum's claims of being a secure building were "maybe not entirely true”.
Mr Marinello, an expert in recovering looted and missing works of art including well-known restitution cases on behalf of foreign governments and heirs of Holocaust victims, told PA news agency: “Let’s face it, we hate to see museums say ‘we’re going to tighten security’ after a theft. Why wasn’t security tightened before? It’s not enough to have cameras on the walls, one needs to properly vet their employees.
“There needs to be sign-ins and sign-outs for every object that’s being studied.
“There are plenty of things that museums need to do and if any museum knows how to do it, it’s the British Museum.”
The specialist also questioned why “one of the most well-funded museums in the world” is having problems with theft. He said it was “too early to know the extent of the damage”.
He said it was now “critical” that the museum can compile a comprehensive list of what has been lost.
“I believe that until they do a proper inventory and compare with previous inventories, they won’t know what is still missing,” he said.
“It’s imperative that they publish a list of everything that might be missing so that it can be recovered.
“It could take weeks, if not months.”
“It’s unfortunate that we entrust these institutions to preserve our cultural heritage, yet we don’t give them the proper funding for them to do so," said Mr Marinello, who founded Art Recovery International in 2013.
The British Museum previously said it will be taking legal action against the unnamed staff member, while the matter is also under investigation by the economic crime command of the Metropolitan Police.
“We have been working alongside the British Museum," a Met Police representative said.
“There is currently an ongoing investigation – there is no arrest and inquiries continue. We will not be providing any further information at this time.”