While most Hounslow house prices are plummeting fast Jasper Conran's home has just smashed Chiswick's sale record.

Walpole House, set on Chiswick's most expensive road, Chiswick Mall, recently sold for £12,500,000.

Bought two years ago for £7,250,000 by one of the UK's most successful fashion designers, Jasper Conran, the property already held the record for most expensive Chiswick sale.

It has been suggested the huge £5,250,000 increase in price that bucks the current gloomy property market trend may be down to the fact that Conran has substantially refitted the interior, adding to the house's already impressive features.

Estate agent, Tony Dalton of Knight Frank in Knightsbridge, who dealt with the sale of the house two years ago, he said: "It is a really beautiful house, I haven't seen it since it has been modernised but is an architectural gem."

The three-storey 18th century house was named after the Hon Thomas Walpole, who lived there from 1798-1803. He was an MP and nephew of Sir Robert Walpole, England's first prime minister. The house, which must be one of the most covetable houses in London, not just W4, then served for a while as the Royal Victoria Asylum for Girls, with the young Queen Victoria visiting in 1838 and describing it as "a most interesting and delightful establishment...for vagrant girls".

In 1840 it became a boys' school, where author William Thackeray studied, leading him to use it as the model for Miss Pinkerton's Academy in his 1847 novel Vanity Fair.

Only earlier this year Conran, who seems to be building on his property portfolio, snapped up Ven House for just under £8.5m, a Grade I listed mansion in Somerset that features nine bedrooms, tennis courts and 34 acres of land - quite a step up from his previous home in Suffolk that he sold last year for £7.25m.

These big money transactions come soon after the discovery that between April and June, Chiswick property prices dropped by a huge 16.5% with the top end of the market being hit particularly hard with no W4 detached houses changing hands at all during the period.

Most expensive property sales in Chiswick since 2000

Address                                                  Postcode          Date                Price
Walpole House, Chiswick Mall           W4 2PS    Aug 17 2006    £12,500,000
Staithe House, Chiswick Mall             W4 2PR    Aug 1 2006      £3,525,000
Barrowgate Road                                  W4 4QS   Jan 31 2008     £3,410,327
56, Woodstock Road                            W4 1EQ   July 17 2006     £3,250,000  
41 South Parade                                   W4 1JS    June 09 2006   £3,210,000
17, Blenheim Road                              W4 1UB    Nov 30 2004    £3,000,000
Strawberry House, Chiswick Mall      W4 2PS    Nov 22 2000    £3,000,000
7 Marlborough Crescent                      W4 1HE   October 2007   £2,900,000
33 Hartington Road                              W4 3TL     July 18 2007    £2,800,000
Morton House, Chiswick Mall             W4 2PS    May  31 2005   £2,750,000