The most expensive luxury penthouse in London is for sale - for $247 million.

But interested buyers won't find the property in any real estate listing. It is offered for sale through personal references and word-of-mouth only.

Penthouse B on top of London's high-end One Hyde Park building is being offered through a "whisper listing." Details about the sale are shared among brokers and prospective buyers only.

Sources with knowledge of the hushed sale said the apartment was being discreetly offered to buyers for about £175 million ($247 million). The whispered price tag for the 18,000 square foot mega-apartment equals about $13,700 a square foot.

The penthouse is in London's posh Knightsbridge and is owned by real estate developer Nick Candy. It has two floors with five bedrooms. Candy lived in the apartment for five years with his wife, actor Holly Valance and their two daughters.

The penthouse features a reception room with double-height ceilings. Glittering Swarovski crystals adorn most of the ceilings. It has a dining room, a Champagne room and a wraparound terrace with views of London's Hyde Park.

One Hyde Park is flanked by ultraluxury establishments such as Europe's largest Rolex store and a McLaren dealership. The building it is in is owned by CPC Group and Waterknights. CPC Group is owned by Candy's brother, Christian Candy, while Waterknights is controlled by former Qatar Prime Minister sheikh Hamad bin Jassim bin Jaber Al Thani.

"Candy hopes to capitalize on this inbound interest and the huge pent-up demand from overseas buyers as Covid restrictions ease and international travel resumes," the head of Knight Frank's Private Office, Rory Penn, said.

Demand for high-end luxury apartments in London and continental Europe has risen despite the pandemic, Penn said. Another apartment at One Hyde Park recently sold for an estimated $157 million.

Last year, London saw $3.7 billion in real estate transactions, overtaking New York and Hong Kong. Penn said property sales in London jumped by 3% last year, while transactions in Hong Kong and New York fell by 27% and 48%, respectively.

"Despite the pandemic, more residential super-prime sales above $10 million took place in London in 2020 than any other global market," Penn said.