According to museum employees and experts in the recovery of stolen items, museum thefts are usually an inside job and are fairly common.

An anonymous employee at a famous London museum called the business "institutionally corrupt," adding that the snatching of some items is considered "Fair game."

According to the worker, "cherished items donated to the museum are sometimes secretly sold off or given to auction houses.

Not everyone who works in museums is on board, by far, but it's an unspoken problem in the industry, according to the worker, citing he was "shocked at what goes on."

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Following the discovery of "missing, stolen, or damaged" artifacts from the British Museum's collection, the latter announced on Wednesday that it had fired a staff member and notified the police.

According to a statement, the artifacts included gold jewelry and gems made of semi-precious stones, as well as glass that dated from the 15th century BC to the 19th century.

The Director of the museum in central London, Hartwig Fischer, said, "This is a highly unusual incident." The museum is best known for having collections that include Parthenon Marbles and the Rosetta Stone.

According to another staff member of another museum, rarely were staff checked by security before leaving the premises, noting that  “It would be easy to take something small without it being noticed for quite a while."

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Dutch researcher Arthur Brand, who has recovered up to £340m of stolen artifacts from around the world, stated that every museum has at one point been a victim of theft.

He adds this is "nothing new," noting that it has been going on "since the beginning of collecting. But in this case it’s the British Museum and apparently a senior collector, so it’s something special.”

Christopher Marinello of Art Recovery International expressed that museum theft was indeed a worldwide phenomenon, but added that museums should not be an easy target for theft since they are "stewards of our cultural heritage."

Experts suggest fortified security measures like CCTV, detailed cataloguing with photo records, as well as intense vetting of workers.

All this aside, Brand notes that full-body searches for employees leaving are "impossible."

A spokesperson for the Museums Association notes that even if theft is not explicitly mentioned in the code of ethics, “museums and the people who work in them should act for the public benefit and with integrity”.

The spokesperson details that not only is theft a breach of law but also a "breach of professional ethics."

“Most people who work in museums really love their collections. They don’t enter the profession with the intention of wrongdoing.”