Gordon's smile is whiter than white

It comes, therefore, as rather a surprise to discover that the Chancellor - not exactly famous for his smile, dazzling or otherwise - has been having his teeth whitened.

The Evening Standard understands he has been undergoing a new treatment called power whitening at a fashionable practice in Belsize Park.

The Chancellor's choppers have apparently been getting the works at the hands of Dr Mervyn Druian. For someone as financially prudent as the Chancellor it is a remarkably expensive business.

Dr Druian, whose clients include such style leaders as the Appleton sisters and personal improvement specialist Cindy Jackson, charges about £650 for a one-hour session which involves painting the teeth with gel, which is then activated by strong light.

Dr Druian, of the London Centre for Cosmetic Dentistry, is understandably reluctant to discuss the Brown teeth. "We see a number of politicians," he said. "I would love to get my hands on Tony Blair. There's a lot I could do with his teeth."

Westminster-watchers have not noticed any major change in the Chancellor's dental appearance of late, but that could be for a variety of reasons. The whitening may only be slight, or perhaps Mr Brown only underwent the process recently.

Most likely, of course, is that the Chancellor simply has not smiled for the past few weeks, and so nobody has noticed. He is currently on holiday in the US, and the intriguing possibility raises itself that Mr Brown is at this very moment trying out his shining new smile on innocent Cape Cod tourists.

It is not the first time that Mr Brown has tried to improve his appearance. For years he used to bite his nails to the quick, but after Labour's 1997 election victory he seemed to have conquered the habit. For a while his nails appeared perfectly manicured, but clearly the tensions of handling the nation's finances were too much for him and by the next Budget he was back to his old ways.

The real question is why the Chancellor has chosen to smarten himself up. "Dental ageing is slow and gradual but people can suddenly reach a stage where they lose confidence in their smile," Dr Druian said earlier this year. "People, especially those between 40 and 60, can see their age in their teeth but feel they can do nothing about it."

The Treasury clearly was not going to shed any light on the matter. A spokesman said: "We don't comment on such things."

However the world of Westminster being what it is, it is hard not to divine an ulterior motive in this uncharacteristic display of personal vanity.

Perhaps it is as simple as his wife Sarah suggesting over the breakfast table one morning that his teeth were not looking their best: or perhaps he really thinks that Tony has to go sometime, and then if only he had a better smile ...