Sarah Sands: Moving to No 10 is the ultimate in social mobility

Lives can be measured in births, marriages and deaths but it is much more interesting to trace destiny and social history through house moves. Each one of them a drama of hope, progress, winding down or disappointment, bubble-wrapped and watched with critical scrutiny by the neighbours. The Camerons' move from Kensington to Downing Street is an intriguing conflict between political achievement and social descent.

The London property market is a Trollopian reflection of social wealth and values. Mayfair, Chelsea, Notting Hill and Kensington are the choice locations of our times for foreign buyers, which puts a spring in the step of native beneficiaries of house prices. The owners of north London Georgian squares are both supercilious and envious about this. Artists go east.

There is also an agreed international design for London houses which is light and open with expanses of stone/wood and as much glass as you can manage. We are all Scandinavian now. Some kind of roof terrace is expected. A view of water is good.

If an estate agent were flogging the No 10 flat, he/she would murmur about it needing some TLC. It's rather better on souvenir stalls than on local shops. Heaven knows where you find a butcher. It is formal and stuffy and just wrong. The White House is for families. Downing Street is for bachelors.

When I interviewed Cherie Blair at Downing Street on the publication of her book, her eyes flashed with bitterness and indignation as she chuckled that "it is a silly little thing, of course" but she had installed a shower. BECAUSE THERE WASN'T ONE. Margaret Thatcher's advice to Norma Major was: " "Don't move in until the new carpets have been put down."

Samantha Cameron held out as long as she could before accepting No 10, and will move to the No 11 flat once it is decorated. We've checked out the Habitat drawers and the pink fluffy beanbag in the newspaper pictures. How much Kensington stuff can she bring with her? She says she is dreading the unpacking. We know the feeling. Will she too be sitting amid boxes of unopened stuff for the next three years?

Moving house is not just about a new life; it also means discarding the old one. I always find the act of moving rejuvenating. The warning that you "can't take it with you when you die" is a kindly promise. I don't even want to take it with me now.

I try to appreciate people who marry their houses for life or who inherit something so beautiful you would not want to move. I lived in one house, far beyond my means, and bestowed anthropomorphic and aristocratic qualities on it. I commissioned a painting of it. It mocks me now that I have shipped out and a new owner is rebuilding it practically from scratch. Through my adult life I have moved, on average, every seven years. All our ambition and aspirations can be poured into a house. Happiness is a new kitchen. It is a fitting reward for Sam Cameron for all the sacrifices she has made.

I am in the middle of a move too. But the first imperative is not a kitchen but broadband and high definition. This is going to be our World Cup television, so no chances can be taken.

The ability to change location to suit circumstances is a privilege that is not universal. Iain Duncan Smith wants the same rights for the poor. Council housing is a reassurance, but also a trap. You are consigned to the same estate for life. Moving house is a great expression of freedom. Lucky old Sam Cam.