Sheikh Khalifa bin Zayed al-Nahyan is one of the richest heads of state in the world. Photo: Getty Images.

A super-rich sheikh has filled the water tanks of an 18th-century mansion he hardly ever visits with Evian mineral water, it has been revealed.

Court documents show Sheikh Khalifa bin Zayed al-Nahyan, the Emir of Abu Dhabi, and one of the richest heads of state in the world worth hundreds of billions made the lavish move at a mansion in Berkshire.

He bought Ascot Place, a grade II listed mansion near Windsor Great Park, Berkshire, for $22m but made extensive renovations and it is now valued at more than $74 million.

As part of the renovation, tanks filled with water were shipped from Evian, France, where the royal family owns several other homes.

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But the sheikh, whose half-brother Sheikh Mansour owns Manchester City Football Club, Sheikh Khalifa has been accused of "profligacy" by the former managers of his vast $6.8 billion London property empire, as part of a legal battle in the High Court.

The directors of Lancer Property Asset Management claim that "apart from the occasional daytime visit," the 71-year-old sheikh, who is rarely seen in public, has never occupied the property.

The court documents show Sheikh Khalifa also had a "very grand" $6 million house with extensive gardens at Ham Gate, southwest London.

But he felt it was too small to house all his staff and security personnel so told his agents to try to buy a neighbour's property but the owner refused to sell.

The Emir of Abu Dhabi has been accused of profligacy. Photo: AFP via Getty Images.

Documents filed in the High Court also allege that Sheikh Khalifa owned several properties, worth an estimated $37 million, in an exclusive enclave overlooking Cannes.

But he abandoned them after he failed to obtain permission for a new palace.

The revelations were made as part of an ongoing legal battle between the directors of Lancer and Berkeley Square Holdings, a set of companies registered in the British Virgin Islands whose ultimate beneficial owner is Sheikh Khalifa and his family.

But lawyers for the Sheikh's companies have accused Lancer of dishonesty and fraud by "siphoning off" about $39 million they received for managing the London estate.

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The lawsuit alleges that Lancer's fees were excessive and that the directors had a "dishonest arrangement" with Mubarak Saad al-Ahbabi, the former chairman of the sheikh's private office.

Lancer's directors, including Andrew Lax, the founder, deny the allegations and say the payments were approved by the president and his family.

They have counter-sued for $13 million in unpaid fees and have claimed unfair dismissal.

The case continues, with a trial set for next May.