Prince Andrew has sold his house for £3m more than the asking price to a Kazakh tycoon with whom he is said to have had business dealings.

Kenes Rakishev, the 29-year-old head of an energy conglomerate, bought Sunninghill Park, Andrew’s former home, for £15m even though it was marketed at an upper guide price of £12m. There were no other bidders.

Rakishev bought the 12-bedroomed house with his father-in-law, a former Kazakh prime minister, using an offshore company. The deal has been kept a closely guarded secret. It is understood that Andrew met the buyers while on a trip to Kazakhstan, a country he has visited on official business three times since 2003, although more frequently in private. He helps broker business deals in the resource-rich former Soviet republic as part of his role as roving ambassador for British trade, a position for which he is not paid. He is also joint patron of the British-Kazakh Society.

Sunninghill, which was a wedding present from the Queen to Andrew and his bride Sarah Ferguson in 1986, had been up for sale for five years before being bought by the Kazakh tycoon eight months ago.

The entire £15m was paid to the trustees who manage the property on Andrew’s behalf. He is the sole beneficary of the trust after his former wife relinquished any claim on the property as part of their divorce.

Artur Krivov, who was the managing director of the UK arm of Rakishev’s conglomerate, Sat&Co, until eight months ago, confirmed a large discrepancy between the asking price and the amount paid.

“I personally was really surprised because there were much better [houses] at that price because I was helping look for a place for them,” he said. “There were other choices which were much more attractive than that. But I guess there were other issues here than just price and the place.”

A source close to Andrew said he understood the Kazakhs had an independent survey valuing the house at about £12m.

A spokesman for Andrew, who said he was in Kazakhstan this weekend on a privately funded “holiday”, said: “The sale of Sunninghill Park was a straight commercial transaction.There were no side deals and absolutely no arrangement for the Duke of York to benefit otherwise or to commit to any other commercial arrangement. Any suggestion otherwise is completely false.”

Explore UK News

• Crime News

• Education News

• Health News

• Scotland News

Times Recommends

• In Margot Fonteyn's footsteps
• Forget beautiful people, let's have wonky Brits
• Fundamentalist brew: faith and power