For more than 20 years, John Nevin was the picture of a dutiful custodian of the nation's artistic treasures, trawling the vast storerooms of the Victoria & Albert Museum cataloguing and organising thousands of priceless objets d'art, from ancient Chinese jade figures to Catherine the Great's diamonds.

The only problem was that Nevin also liked to take his work home with him.

To be precise, his "taking home" involved sneaking some 2,068 items out of the museum of decorative arts in London and using them to embellish the three-bedroom council house he shared with his wife in Chiswick.

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When police raided the property, they found his bathroom curtains had been fashioned from a length of stolen rare cloth and his wife had been carrying her groceries in a 19th-century Italian leather and tortoiseshell handbag.

The full story of the prolific pilfering from one of the world's richest collections, conducted when Nevin was working as a backroom assistant at the V&A between 1944 and 1953, can be revealed for the first time after confidential police files were released to The Independent under the Freedom of Information Act. The case remains the largest-ever theft in quantity from a British museum and dozens of items are still missing.

Documents held at the National Archives in Kew, west London, reveal that Nevin was able to slowly remove his haul from the storage areas of the museum – smuggling out items such as a small table, which he dismantled and secreted bit-by-bit in his trouser leg – after he was granted unique access to showcases in the aftermath of the Second World War.

By the time police caught up with the kleptomaniac museum worker, who was 48 when he began his crime spree, Nevin had amassed a vast array of precious objects, including 20 Japanese silver sword guards, 229 illustrations torn from books, 18 pieces of Albanian embroidery, 132 original drawings and watercolours and a 300-year-old Flemish tapestry.

Nevin profited from the opportunity presented when elements of the V&A's collection were returned to its building in Kensington after the war, when they had been in storage.

Senior managers at the museum were shocked when the string of thefts was discovered late in 1953, the documents make clear. In his statement to police, Peter Floud, Nevin's boss and head of the Circulation Department, the part of the museum responsible for external loans, said: "His duties involved moving, handling, sorting and checking museum objects. As a result of the war years, when stocks were being moved into shelters and then back to the museum, a great deal of sorting was necessary.

"Nevin was employed on this work. He was entrusted with keys to showcases and cupboards, and as a trusted servant of the museum, he was allowed to work mainly without supervision in the checking and sorting of exhibits."

Armed with his set of keys, Nevin set about systematically removing items that caught his fancy, including a Spanish engraved flintlock blunderbuss which he hid in the eaves of his attic and a collection of rare watches, which found a new home wrapped in canvas in his toilet's cistern.

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The disappearing loot was finally spotted when a stocktake in 1953 began to reveal a list of missing items with which Nevin was the only employee known to have worked. Police were called to the small house the museum worker shared with his wife Mary, 9 Nightingale Close, Chiswick, in March 1954 and rapidly set about dismantling the treasure trove inside.

Initially, the couple denied any knowledge of the missing objects, repeatedly telling the two detectives in charge of the case that items in their home had been bought second hand or were wedding presents. When a leather and tortoiseshell handbag (later found to be the rare 19th-century Italian work) was shown to Mrs Nevin, she said: "That's my shopping bag. I bought it in a shop."

But as the officers began recovering objects from increasingly unusual hiding places – a gilt figure of a knight secreted behind a hot water tank, musical instruments found in floor joists, a silver ink pot hidden in a chimney and several carved jade figures found in a vacuum cleaner dust bag – the couple's united façade of innocence began to fall away.

The documents record how Mrs Nevin, who later pleaded guilty to 10 charges of receiving stolen goods, broke down in front of detectives and began berating her husband. She said: "You see what you have done. You would not listen to me. You pushed me into the background. I was just a nonentity. I told you not to keep bringing stuff home. You will get into as much trouble as if you had stolen a thousand pounds." When officers returned to spend a second day removing the haul, Mrs Nevin added: "I am glad it is over really. I have been worried for years. We stopped asking people in because they used to say how expensive the things were."

The extent to which the house had been almost entirely furnished with the contents of the V&A storerooms is revealed by a statement summing up the case following Mr Nevin's conviction on 24 charges of theft: "Practically everything in Nevin's small three-bedroomed council house, with the exception of the bed linen and items of clothing, was found to be property stolen from the museum, so that at the end of the search the rooms were practically bare."

A devastated Nevin, who made an "ineffectual gesture at suicide" by drinking half a glass of cough mixture shortly after his arrest, was sentenced to three years' imprisonment at West London magistrates' court in June 1954. The judge noted that he had asked for the theft of 2,042 other items to be taken into consideration. Mystery surrounds the fate of other objects believed to have been stolen by the one-time assistant. In a (vain) attempt to secure a pension, Nevin returned to the museum following his release from prison in 1957 with a collection of 29 spoons and other valuables he claimed had been missed in the police search.

A detective inspector dealing with the case wrote: "Nevin was aware that there are still some thousands of pounds' worth of property missing from the museum stolen during his 20 years of service, but declared that all he had ever illegally taken had now been returned to the authorities. He said his only object in returning the property was to enable him to make a new and honest start in life."

The documents conclude by noting with some satisfaction that Nevin is living in "straitened circumstances" on "£3 a week allowed to him by the public assistance authorities".

For his part, the museum worker with a wandering eye offered only one explanation for his crime spree. He said: "I couldn't help myself. I was attracted by the beauty."