For decades it lay gathering dust under the living-room sofa, a forgotten family heirloom brought to Britain from China by a long-lost relative.
But a recently rediscovered bowl has turned out to be a Qing dynasty masterpiece, made to mark the birthday of a Chinese empress dowager in Beijing’s Forbidden City.
And the rare imperial relic is now set to sell at auction for £20,000 to £30,000.
The huge porcelain dish, which has a circumference of two feet and weighs 30lb, was brought from China by Wing Lung Goo in the early 20th century and has been passed down generations of his family.
For years it has been stored under the sofa of one of Mr Goo’s descendants in Barnet, north London.
The relative had a hunch it might be something special when they found it and contacted auctioneers, sending them photographs of the dish, which is decorated in imperial yellow with green and aubergine enamel elements.
John Axford, an Asian art specialist who appeared on BBC's Antiques Roadshow, said he was intrigued by the object due to its size, and arranged to visit the townhouse to view it.
Mr Axford found a four-character seal mark on its underside stating 'Chuxiugong zhi,' or 'Made for the Chuxiu Palace'.
The Chuxiu Palace, also known as the 'Palace of Assembled Elegance', was one of the six Western palaces located at the Inner Court of Beijing's Forbidden City.
The rare Chinese imperial relic is set to fetch up to £30,000 at auction
The dish, produced to mark the birthday of a Chinese empress dowager, is decorated in imperial yellow with green and aubergine enamel elements
It had been stored under the living room sofa of a descendant of Chinese immigrant Wing Lung Goo, who brought it to Britain
Mr Axford concluded that the dish had been produced to mark the birthday of the Empress Dowager Cixi in the 1880s, but said the family were likely to have hidden it away as it was too large and heavy to display safely on a wall or shelf.
He said: 'We are not exactly sure why the dish was kept under a sofa for decades, but it could be that it was too big for them to hang on a wall or display.
'It is not necessarily the most sensible place to store something like this, and when we were sent photos of the dish it was covered in dirt.
'But the size of it meant I thought I should go along and see it, and when studying the dish I identified the very unusual seal mark that was used specifically for dishes made for the empress's birthday.'
Mr Axford, chairman and head of the Asian art department at the auctioneer Woolley & Wallis, added: 'Once it was cleaned the dish has come out beautifully.
'To discover an imperial dish of such monumental scale in near pristine condition and learn that it was stored beneath a living room sofa in London is truly extraordinary.'
The dish – described as among the 'most significant examples' of late Qing palace porcelain to come up for auction in recent times – is painted with two confronting dragons contesting a flaming pearl among pin clouds and flames.
Around the outside is a floral border with lotus, prunus, peony, chrysanthemum and hibiscus flowers, while the rim is decorated with a further six dragons and flaming pearls.
Woolley & Wallis said the 'rare' dish was the 'only known example of this type, where the base is also glazed in a yellow colour'.
It added: 'Combining imperial palace provenance, direct association with the court of the Empress Dowager Cixi, exceptional scale and a potentially unique yellow-glazed base, the dish ranks among the most significant examples of late Qing palace porcelain to appear on the market in recent years.'
The Qing dynasty, which ruled from 1644 to 1912 under the leadership of the Manchu people, was the last imperial dynasty of China.
The item is set to go on sale on November 10.