Rutland Gate Property
This £300m property in Knightsbridge features 45 bedrooms and is thought to have bullet-proof windows Reuters

A Knightsbridge mansion previously owned by Rafiq Hariri, the late prime minister of Lebanon, has gone on sale with a record £300m price tag.

Property insiders said that the seven-storey house, being offered to a select list of wealthy international billionaires, was likely to become the most expensive home in British history.

The 60,000 sq ft building, which overlooks London's Hyde Park, has 45 bedrooms and apparently boasts bullet-proof windows.

Gary Hersham of London agents Beauchamp Estates said: "It is a trophy piece in a remarkable location. The views across the park are spectacular."

The luxury home was passed as a gift to Sultan bin Abdulaziz, crown Prince of Saudi Arabia, after Hariri was assassinated in 2005.

It has now been put on sale following Abdulaziz's death in October 2011.

Agents said the mansion was originally built as four separate family homes but had been converted into one of the capital's largest domestic properties.

The stucco-fronted Regency residence now runs from No 2 to 8a Rutland Gardens and features a large swimming pool, a vast industrial-sized catering kitchen, underground parking and three lifts.

If the property sells for the £300m asking price, it will more than double the previous record set by Grade II-listed mansion Park Place near Henley-on-Thames.

That 300-year-old property was sold in 2011 for £140m and eclipsed the £136m paid for a penthouse apartment at the One Hyde Park development in Knightsbridge in 2010.

Charles McDowell, a London-based consultant specialising in high-end residential property, said: "You are going to have to wait a long, long time for something like this to come on the market again."