Bruce Anderson: And now, may I present the only serious candidate for leader of the Tory party...

David Cameron is a class performer, in the way the term is used of a promising cricketer

So it is easy to identify the candidate. He would have David Davis's background, William Hague's experience, David Cameron's looks and personality, Ken Clarke's blokishness and Malcolm Rifkind's platform skills. Only one little problem remains. There is no such composite paragon. In his absence, the Tories will have to make do with the best candidate available. There is an obvious choice.

David Cameron has defects. He is only 38, he went to Eton and he can come across as too metropolitan. But these are trivial points. A man of broad human sympathy, his considerable knowledge of his country and countrymen is not confined to London. As for youthfulness, that is one fault which time is guaranteed to cure.

Eton: it is odd how otherwise intelligent persons can develop a complex about that establishment and talk as if its sons were members of a different species. It seems as if there are three types of schools in this country: state ones, public schools and Eton. It should not matter where a leadership candidate went to school, more than half his life ago, yet there is one unfashionable point to be made in favour of Eton. It does instil self-confidence. So if there were to be a young leader in stressful circumstances, an Eton education could have advantages.

There are other unfashionable points to be made on David Cameron's behalf. In earlier years, he was a political advisor; before that, he worked in Tory Central Office. It is hard to know which is the more derided profession - or which is more unfairly mocked. Both roles can provide a young politician with invaluable experience.

As a political advisor, David Cameron started off with Norman Lamont. Mr Lamont had sound policies in place. He was right to insist that the green shoots of economic recovery were sprouting. But he received no political credit and was sacked. David Cameron then moved to the Home Office under Michael Howard.

Mr Howard was the most right-wing Home Secretary for many years. He was determined to repudiate the institutional pessimism of the Home Office, which insisted that nothing could be done to prevent the rise in crime. So Mr Howard ought to have been the popular press's hero and the public's darling. He was not. Again, David Cameron had a good vantage point to observe political failure: useful training for an apprentice politician. If you hope to have the chance to succeed, it is helpful to work out why others failed.

A political advisor ought to combine stamina and affability with good judgement and a sharp intelligence. On policy questions, he has to be taken seriously by able senior civil servants who have been doing the job for years. He must also persuade everyone that his political points are useful insights, not youthful exuberance. If he cannot do all that, he will rapidly lose traction. As long as his minister is kindly, he may still be heard. But nobody will be listening.

David Cameron did extremely well. He was very good at explaining complex policy questions while always seeing the political angle. He respected the good civil servants he came across, without going native. They in turn acknowledged his political feel and his brain power; at Oxford, he took a first without being a slave to his books. Michael Portillo, himself a former political advisor, said that David Cameron was the best one he had ever seen. Even so, it is a huge step from giving advice to running for the premiership. David Cameron's ability to perform at the highest level would have to be taken on trust.

A lot of Tories are now prepared to do this. They think that he has class, and it has nothing to do with Eton. They mean that he is a class performer, in the way the term is used of a promising young cricketer. He may not yet have scored many big hundreds, but every time he bats, there is electricity. You can tell that he does not just want to make runs. He wants to dominate the bowling. That is the player to pick.

Back in July, when David Cameron had decided to play the campaign long, David Davis's supporters put it around that he was merely a bland, left-wing moderniser. Bland is not a description which those who know him would recognise. They also wondered how a left-winger had worked so happily for Norman Lamont and Michael Howard.

As for being a moderniser, Mr Cameron is not an ideologue. He has no respect for the radicalism of easy answers. He believes that Toryism should be an unending dialogue between old principles and new circumstances - rather like Britain itself. But his instincts and prejudices are thoroughly Tory.

David Cameron has other qualities. Although a committed politician, he has a full life outside politics. That would commend itself to the voters, who are rightly suspicious of one-dimensional politicians. He has a splendid wife, Samantha, a successful businesswoman as well as a good painter. Their eldest son, Ivan, is dreadfully handicapped with a rare condition which condemns him to prolonged painful fits, brain damage and the life of an invalid.

Because of Ivan's illness, David and Sam have had endless night-long vigils in Great Ormond Street hospital. They never complained. The child's survival has been a medical miracle. Some of their friends have wondered whether old-fashioned medicine might have been better. His parents would profoundly disagree. They have responded to affliction with such strength and grace that it has ceased to be an affliction. They are determined to bring happiness into Ivan's life. Whether it is soft toys or gurgling at the pigs on the neighbouring farm, they are always searching for ways to give him interludes of pleasure amidst all the suffering.

This does not mean that Mr Cameron is qualified to be Prime Minister. It does refute the nonsense that he is some shallow Notting Hill trendy skating on the surface of life.

David Cameron is young and untried. He is also able, decisive and likeable. He is cut from big timber. The alternative candidates, Ken Clarke and David Davis, would pull the party back to the past. In recent years, two vital words have vanished from the Tory vocabulary, and only David Cameron could restore them: hope and future. As Margaret Thatcher would have said, there is no alternative.