A series of thefts by an attendant at the Victoria and Albert museum went unnoticed for around two decades, according to National Archive records.
Poor security in the V&A allowed thefts to go on for around 20 years
The thief, a man called Nevin, stole 2,544 items from the museum, prompting a security report in 1954.
A subsequent stock-take revealed about 5,000 objects were missing, although not all were attributable to Nevin.
No stock-taking had taken place for 16 years - not since 1937 - prior to the discovery of the thefts.
Details of the thefts came to light in files now released by the National Archives at Kew, in London.
Objects taken included musical instruments, ceramics, prints, oil
paintings, lacquer boxes and 98 Japanese swords.
Nevin also managed to take two imitation 18th century French tables.
said they had no idea how he managed it, although they showed "signs of being
dismantled" when they were recovered.
A report into security at the museum stated: "At least some of these objects were known to have disappeared from the museum not less than 20 years before: others had been in the museum within the past few months."
It concluded: "It is difficult to put any monetary value on the losses, but on the basis of the objects so far recovered, the total value... is unlikely to be below £15, 000, and the net loss will probably amount to several thousand pounds."
Nevin, who worked in the museum's circulation department, was later sentenced to three years in prison for the thefts.
A document in the file reads: "These thefts appear to have started before the last war, and the total number of objects recovered from Nevin by the police number 2,544, of which about 100 are so badly damaged as to be probably beyond repair, and must accordingly be written off."
After valuations on the cost of the items lost due to damage, it concluded the museum must "ask for the Treasury authority to write off articles to the value of £2,800".
Nevin had been at the museum since 1930 and worked in the circulation department from 1935, with a break of five years during the war when he was seconded elsewhere.
It seems he stole items from various parts of the museum, including the circulation department, the library, and the metalwork, woodwork and ceramics departments.
His home was searched after several items were found to have gone missing from the museum, prompting the discovery of more than 2,000 items.
The report into how the thefts were possible criticised the lack of security measures in place at the museum.
It recommended regular and random stock-taking, as well as secure locks to be placed on objects.