The 70-carat Idols Eye will have its fate decided by a London court (Picture: Champion News)

A royal family feud over a prized diamond which could be worth up to £21 million is set to be thrashed out at the High Court.

Rival members of Qatars multi-billionaire Al-Thani dynaysty are fighting over the Idols Eye, said to be worlds largest cut blue diamond.

The 17th-century, 70 carat gemstone, found in India in 1600, was once owned by a Sultan of the Ottoman Empire and after WW2 was set as the pendant to a necklace containing 86 other diamonds.

It is now in the London home of the late Qatari culture minister Sheikh Saoud bin Mohammed Ali Al-Thani, who bought the stone in the early 2000s and died in 2014.

Shortly before his death, he lent the Idols Eye to Qipco, an investment company owned by art collector Sheikh Hamad bin Abdullah Al Thani, a cousin of Qatars ruler.

Sheikh Hamad bin Abdullah whose $400m Mayfair home Dudley House is reportedly Britains most expensive private residence claims he has the right to buy the stone for US$ 10million (about £7.8m).

The loan agreement is said to have given him the option to buy it with the consent of Elanus Holdings, a company handling the estate of the widow and children of the late Sheikh Saoud.

Sheikh Hamad bin Abdullah is fighting the late Sheikh Saouds widow and children for the diamond (Picture: Champion News)

The two sides disagree over how much the stone is worth and whether there was ever an agreement to sell it.

Qipco claims the sale process was kicked off in 2020 with a letter from Elanus Swiss solicitor.

It stated: I just learned from Sheikh Hamad, the son of the late Sheikh Saoud Al Thani, that the family would like to sell the Idols Eye.

Qipco claims it continued with the process but that the late Sheikhs family went back on the offer, which wasnt allowed under the loan agreement.

Its asking the court to order Elanus to sell the diamond for $10 million, which is the upper end of a previous valuation by Christies.

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Elanus lawyers say it was a mistake to take the letter as an offer to sell, arguing it didnt state the companys wish to get rid of the diamond.

The Idols Eye was previously owned by an Ottoman sultan (Picture: Champion)

Although the 6 February letter said that the family wished to sell the Idol’s Eye, they did not, the High Court was told.

Indeed, they had not even discussed or considered it.

As for Elanus and its ultimate beneficial owner, the Foundation, they had not even been consulted, let alone formed any wish.

Elanus said the letter was sent after the late Sheikhs son had thoughts about selling the diamond to fund property deals.

Its also arguing the gem could be worth far more than $10 million, citing an Elanus diamond experts valuation of £21 million.

Qipcos lawyer said Elanus had in fact become fixed with the wish to sell and that their Swiss solicitor had clear authority to send the letter.

The solicitor had an unambiguous instruction to write a formal letter as the representative of Elanus informing Qipco that we wish to sell the Idol’s Eye, the lawyer argued.

Qipco argued the higher valuation by Elanus diamond expert was just an attempt to raise the sale price.

The hearing continues.

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