Bruce Anderson: Boris Johnson is a libertarian, but he is not a Tory - and he's unlikely to last the course

He is a man without core belief: without a political or intellectual compass

Gordon Brown could still recover if at least two out of the following three events were to occur. The first is the return of economic feel-good. The second, a transformation of his and his senior colleagues' personalities, so that when they address the public, they no longer sound like a convention of speak-your-weight machines, spiked up by the occasional Dalek. Finally, Gordon Brown needs David Cameron to commit a succession of gaffes.

None of that will happen. Instead, the electorate will grow more and more irritated, as if dealing with a grossly overstaying guest who ignores every hint to depart. It will soon be time for Mr Cameron to reprint a bumper-sticker last seen in the late Seventies: "Cheer up, the Tories are coming".

Cheering up, gaffes; Boris Johnson. A few weeks ago, prominent Tories were asking themselves which would be worse: Boris losing or Boris winning. Even on Friday, as the scale of the Labour defeat became apparent, some Tories wondered whether it would matter if Boris was defeated. There was a large Tory cake already. Did it really need to be crowned by a cherry with a self-destruct mechanism?

At the beginning of Boris's campaign, some of his own advisers sounded like a housemaster's report from a generation ago. "Boris has shown signs of improvement. I only had to beat him three times this term. But he is still far too ready to play the fool. On a bad day, he can be a bigger nuisance than any boy in the school." There was a further anxiety. Did Boris sincerely want to win or, when he had lost narrowly and hilariously, would he turn to his agent and say: "That was fun. Now: 50 per cent extra on all my fees?"

Then everything became serious and so, to widespread surprise, did Boris. He not only had his hair mown; he kept his tongue curbed. Much of the credit is due to Lynton Crosby, the Australian political enforcer. Whatever caused Mr Crosby's ancestor to be transported, it must have been something formidable. In 2005, Crosby advised Michael Howard's Tories to talk about immigration in a way that attracted right-wing voters without alienating the more liberal-minded. This was the "dog-whistle" technique: a sound audible to the dog which would not grate on passing humans. In 2008, Mr Crosby moved on, from the dog whistle to the dog lead. He kept Boris under control.

Lynton Crosby's ticket-of-leave has run out. He is returning to Australia. This creates a vacancy. Now that Bertie Wooster is in City Hall, who will be Jeeves? It is a vital role, for unless Boris has undergone the sort of personality change which might save Gordon Brown, there is a basic problem. He is a man without core belief: without a political and intellectual compass.

He does have core instincts: three of them, two attractive. He is a libertarian and a hedonist; he is in favour of everyone having a good time, especially himself. But he is not a Tory. There is no reverence for institutions or tradition: no interest in history. Tories approach British history with a mixture of sentimentality, allegiance and hard thinking. Boris's response to that would be derisive laughter. If he were 10 years younger, he could easily have been seduced by Tony Blair, another man who uses charm as a substitute for intellect and reliability.

Boris's third, less attractive core instinct is selfishness. Just below the bumbling exterior lies a ruthless ambition and an almost complete lack of interest in anyone else's well-being. Up to now, he has been able to get away with this by exploiting his charm. Over the years, Boris has convinced himself that he can charm his way out of any blunder, any inconvenient commitment, any deception. To be fair to him, it has worked: thus far.

It will not be enough to see him through the next four years. Mayor Boris has two assets: the ambition – he will not want to fail – and a brain. Narrowly missing a First in Greats, he did not fall short because of stress arising from overwork. Yet there is one problem with the brain. It has hardly been used. Boris has never written a closely argued article: never tried to think his way through a complex intellectual question. When he is not clowning and goofing, he is remarkably inarticulate. He will take a dart at an issue, offering his solution in a slangy stumble. When someone points out the obvious flaws in his suggestion, he quickly becomes peevish. From now on, he will have to do better than that.

Fortunately, the Mayor has few powers. Boris can concentrate on planning, transport and crime. As regards planning, he has some further good instincts. Detesting old London, bourgeois London, Imperial London, Ken Livingstone was happy to violate its skyline. Though he will not find London brick and leave it marble, Boris believes that it should be the Flower of Cities. He will have to work out how to reconcile aesthetics and economic development. This means listening to the experts without accepting everything that they say. It means lots of meetings, hours of concentration, evenings of paperwork. Above all, breaking the habit of a lifetime, it means thought.

The same will be true of transport. On crime, however, where he has much less executive authority, Boris's qualities might prove useful. London's crime crisis could only be brought under control by a myriad of local initiatives. Mothers who do not want their sons to join gangs and carry knives: council estate residents who are fed up with drug dealers and who want their sink estate to swim: men who have come from the mean streets, sometimes via prison, and who are now desperate to discourage youngsters from repeating their mistakes. Boris could be the Mayor to encourage all those active citizens. He could use the Mayoralty as a bully pulpit on crime.

He must also ensure that there are more police, deployed much more effectively. London also needs a new Metropolitan Commissioner. Ian Blair, the small change for Tony Blair, lacks the moral depth to give his force proper leadership.

Crime brings Boris one further advantage. A number of Ken Livingstone's lefty intimates made off with public funds. Their offences could take six months to expose. That will give Boris the political initiative and, as it were, time to think.

But there should be no long delay in turning thinking into results. This weekend, some Labour MPs were finding consolation – in Boris. A year from now, they hope to be saying: "Twelve months ago, the voters of London chose an Etonian, a toff twit in a Bullingdon Club tailcoat, to be their Mayor. They would not vote that way today. The country should not repeat their mistake."

If Boris's mayoralty did slide giggling beneath the waves, the embarrassment could damage the Tories' prospects. Conservatives must hope, therefore, that the less Wodehousian aspect of his character become apparent, which they may. In contrast to Gordon Brown, it is not certain that Boris will fail.