Sarah Sands: Why street art knocks spots off a bust of Churchill

One of David Cameron's natural advantages is a wife who understands non-essential shopping. Samantha Cameron's mother, Annabel Astor, packages taste to insecure Londoners through her home furnishing company OKA. Samantha designs for Smythson, which brilliantly worked out that what Sloanes love best in stationery is bright colours and jokes.

So the prezzie list from the British Prime Minister to the American President was never going to be a slog. It was pure Sam Cam, Sloane Street with a funky edge. Hunter Wellingtons raise a yelp of joy in Cornwall or Hunstanton. Scented candles must be the most popular gift among the Harvey Nichols classes, back and forth, perhaps never even opened.

So far, so conventional. The Ben Eine artwork is where Samantha Cameron gets her bohemian reputation. The Banksy pupil makes art out of graffiti. But it is really Shoreditch chic rather than anything more threatening. Banksy's biggest fan base is among the professional classes.

As a present to the President it is about the future not the past, as far as you can get from a bust of Winston Churchill, the present given as a gesture of solidarity after 9/11 that was so unwelcome in the Obama White House that it was actually returned.

All official presents are statements about the giver as well as the recipient. For every disappointed spouse or child who complains of too little thought or money, a statesman is far more devastated by a poor gift. No wonder Gordon Brown felt humiliated by his box set of DVDs from President Obama.

It was characteristic of Brown's fortunes that his exquisitely chosen presents for the President looked so laboured and formal by contrast. A pen-holder made from the timbers of an anti-slave ship, the sister vessel of that whose timbers were used in the Oval presidential desk. And a first edition biography of – Churchill, again.

The last leader to try as hard as Brown was probably Edward Heath before his audience with Chairman Mao. According to Philip Ziegler's biography, the former prime minister studied Mao's interest in Charles Darwin and sent William Waldegrave to try to wrest from the Darwin family a copy of Das Kapital inscribed from Marx to Darwin. The family refused, but did give up a signed photograph of Darwin, to which Heath added a first edition of The Descent of Man. First editions suggest a hunt by the giver and erudition in the recipient.

In the exchange of presents between the Obamas and the Queen, the presidential gift of an iPod, full of meaningful tunes, was thoughtful. The Queen's offering, a signed photograph of herself and Prince Philip was dull by comparison, but more desirable. After a life time of giving and receiving official gifts, she knows what works.

I am always begging relatives and friends for framed photographs of themselves, although it might be de trop to have them signed. I have also learnt that you can buy men the most dazzling presents but what they really want is socks. And that young married couples don't want interesting presents, they want John Lewis.

The presents between Cameron and the Obamas were significantly well matched – unstuffy, friendly, cool. The Obamas' gifts, including a signed lithograph by veteran LA pop artist Ed Ruscha, were more expensive, but then to borrow a phrase, Cameron was the junior partner. The last lesson of presents is that the only thing worse than being mean is being competitive.

Sarah Sands is deputy editor of the London Evening Standard