What is London’s best address?

The ultra private street in Kensington W8 beat contenders such as Eaton Square, Chester Square and Cadogan Sq in Belgravia, Mayfair’s exclusive enclave Albany, Bishops Avenue, Hampstead, and The Inner Circle, Regents Park.

The criteria for choosing the tree lined private road which runs from High Street Kensington to the South to Notting Hill Gate was to find the London street with ultimate security, seclusion and rarity value.

Tim Wright, Head of Knight Frank’s Kensington Office, said: “For sheer exclusivity this street beats all others in London. Owned by The Crown Estate it is unparalled in providing an enclave of substantial detached villas offering such a high degree of security. Both street entrances guarded by 24-hour security and adjoining properties include Kensington Palace itself.”

“Because private homes very rarely come onto the market they are almost immune from the rest of the London property market and command exceptional prices. You can expect these houses to sell at a rate of £2,000 per sq ft. The properties vary in size but are generally in the 15,000 to 20,000 sq ft bracket so a family house with staff accommodation can sell for between £18m-£40m.”

There are calculated to be no more than 20 private dwellings in Kensington Palace Gardens and Palace Green (continuation of the same road), including a few apartments at No: 8, and if they come up for sale they are very rarely publicly marketed.

FACT BOX: Kensington Palace Gardens, known as Millionaire’s Row, is behind Kensington Palace, the birthplace of Queen Victoria and the former home of Diana, Princess of Wales.

The road was laid out in 1843 and lined with mansions built by distinguished Victorian architects such as Sydney Smirke and Charles Barry who designed the Palace of Westminster.

The street contains Britain’s most expensive house at 18-19 – a former embassy that came onto the market with an asking price of £85m in 2001. Its owner, an Iranian art-collector, is believed to have sold it for far less to the F1 racing supreme Bernie Ecclestone.

The 55,000 sq ft house is an eastern palace complete with prayer room, walls of Islamic mosaics and an indoor swimming pool inlaid with a classic Persian carpet design. There is underground parking for 20 cars, a Turkish bath, hairdressing salon and enough space for a small harem.

Any private buyers will find themselves neighbours of some of the world’s wealthiest individuals, including The Sultan of Brunei.