A Sri Lankan jewellers' organisation claims to have solved an enduring secret surrounding the engagement ring of royal fiancee Kate Middleton.
The famous sapphire at the heart of the ring came from a mine in the centre of the country 35 years ago, the Sri Lanka Gem and Jewellery Association says.
Royal jewellers Garrard refused to comment on the claims.
Prince William gave the ring to Miss Middleton in October. It was first worn by his mother Princess Diana in 1981.
A spokeswoman for Garrard told the BBC that the origins of the precious sapphire and blue diamonds in the ring - and their value - remained a closely guarded secret.
"All I can say is that it is a stunning ring befitting of a royal engagement," the spokeswoman said.
'Deep intense blue'
The sapphire at the centre of the ring is officially called the Ceylon Blue Sapphire, Sri Lanka Gem and Jewellery Association committee member Abdul Rahman Sheriff told the BBC Tamil service.
He said it was originally mined as a 32-carat uncut gem before being re-cut to 18 carats and sold to a gem dealer in Colombo.
Mr Sheriff said the dealer then sold it on to a Canadian jeweller who re-cut it into a 12-carat stone and in turn sold it to Garrard - the royal jewellers in London.
Garrard then mounted the gem on a ring surrounded by diamonds, he said, before placing it alongside other rings for Princess Diana to choose from for her engagement to Prince Charles in 1981.
The ring was presented by Prince William to Kate Middleton when the pair became engaged while on holiday in Kenya last October.
Mr Sheriff said that he was convinced his association could definitively trace the sapphire's journey from its discovery in Matale district to its eventual arrival in London - although there is no way of independently verifying his claims.
"Deep intense blue combined with their high lustre makes Sri Lankan sapphires very distinctive while also making them the most sought after... in the world," he told the BBC.
He said that the value of the sapphire was about $25,000 when it was mined - but its estimated market value today was in the region of $600,000.
The Sri Lanka Gem and Jewellery Association says the royal wedding has significantly boosted sales of Sri Lankan sapphires, and that worldwide demand now far outstrips supplies.
Gem mining is a seasonal activity in Sri Lanka and employs about 100,000 people - two-thirds of the island are believed to have the potential to contain gems.
Sri Lanka is known to produce more than 50 varieties of gem stones - second only to Brazil - and is believed to account for about 25% of global sapphire sales, worth an estimated $350m annually.