Property market sources said the value of the deal, whose details were jealously guarded by both the seller and buyer, was around Bt950,000 per square wah for the 8.870 rai property put on sale by the Britain's Foreign and Commonwealth Office (FCO) in one of Thailand's largest property sales ever.

The FCO declined to give a figure for the property sale, indicating only that it had completed the transaction with Tiang Chirathivat Real Estate, part of the Central Group, which owns a neighbouring flagship retail property.

The embassy compound is located in Bangkok's prime business district, at the intersection of Wireless and Ploenchit roads.

"This is the largest ever property sale by the Foreign Office. The historic residence, the embassy and the 'green character' of the compound will, however, be preserved," said a statement from the embassy.

The embassy originally occupied about 31 rai of land that had been purchased in 1922 from Phya Pakdi Noraset (Nai Lert). There had been talk of the sale of part of the property for over a decade, but it was not until late last year that bidding was opened on about one-third of the block.

"About £11 million of the proceeds will fund redevelopment of the remainder of the compound, including new staff accommodation, recreational facilities, remodelling of the embassy offices and security works.

"The balance will pay for vital investment elsewhere on the FCO's worldwide estate," the embassy said.

There were several bidders interested in acquiring the property such as Charoen Sirivadhanabhakdi, of Chang Beer fame, Land & Houses Group, Hong Kong Land and Central Group. Richard Ellis was appointed as broker.

Land & Houses, Hong Kong Land and Central Group were short-listed for the final bidding. Land & Houses was reported to have made a bid of around Bt700,000 per square wah. Later it withdrew its bid altogether.

Central Group won the bid with its offer of about Bt950,000 per sq wah. Property sources said Central plans to use the plot to build a five-star hotel, a luxury retail complex and an office building.

The two main residences on the embassy compound have already been demolished to make way for the sale. The War Memorial Statue of Queen Victoria, in the middle of the compound, will be moved to an appropriate place within the compound.