It would be hard not to feel sympathy for Gordon Brown, although some people are managing that task pretty well. In terms of intellect, seriousness and experience, Gordon Brown is still the best qualified of the members of his own Cabinet to be Prime Minister. David Miliband and Jack Straw are the most plausible alternatives, but neither is a formidable candidate, or likely to win the next general election for Labour.

Though it is now a long time ago, Gordon Brown's first Parliament as Chancellor, from 1997 to 2001, was deservedly successful. He was wrong to damage the private pension system by introducing a stealth tax, but he was right to give the Bank of England independence on monetary policy, and to keep Britain out of the euro. He was also wise to follow Kenneth Clarke's Conservative expenditure plans.

In his second and third terms as Chancellor he was more political and less effective; he allowed government expenditure to rise under the misleading name of “investment”, which most of it was not. He obstructed Tony Blair's proposed reforms of health and education. He was one of those chancellors, like Nigel Lawson, whose misjudgments, though significant, have to be set against important achievements.

In his speech on the scaffold Charles I observed that: “A subject and a sovereign are clean different things.” That is certainly true of a chancellor and a prime minister. Since 1945, only four chancellors of the exchequer, out of a possible 21 have gone on to become prime minister. They were Harold Macmillan, James Callaghan, John Major and Gordon Brown; not a wholly reassuring list.

The talents required of a prime minister, particularly the political talents, are very different from those of a successful chancellor. Of course there have been chancellors who might have made excellent prime ministers, but never reached the top job.

They tend to have been centrists such as Rab Butler, Iain Macleod, Denis Healey or Ken Clarke. Nigel Lawson, although an important Chancellor, was probably too individualist to become prime minister.

It is often said of self-made men that they “made their own luck”. In the year since he became Prime Minister one could fairly say that Mr Brown has made his own bad luck. He inherited the consequences of his own economic policies. For ten years he controlled financial policy with an iron fist. He had an agreement with Tony Blair that economic policy should be left to him as Chancellor.

In any case, Tony Blair never showed any sign of competence in economic policy, or of taking much interest. Even his property speculations became a public joke.

Mr Brown's big mistake was that, as Chancellor or Prime Minister, he failed to foresee the crunch that lay ahead; indeed, he boasted that he had abolished “boom and bust”. It was always an obvious danger. In 2000, I was involved in formulating the investment policy of a large charitable fund. All of us saw that there was a threat of a big downturn ahead. We based our investment policy, successfully as it turned out, on protecting the fund against the downturn whenever it should come.

At the Treasury, Gordon Brown must have been warned of the risks. Yet he raised spending in the spirit of the US Admiral David Farragut: “Damn the torpedoes. Full speed ahead.” A high proportion of Brown's present unpopularity can be attributed to stagflation, with its painful combination of rising costs and falling income on a national scale. The torpedoes have struck.

There have also been specific blunders in his year as Prime Minister. He should not have allowed the expectation of an early general election to run away. In 1955 Anthony Eden did use his honeymoon period as Prime Minister to call an election which increased the Conservative majority. Yet a prime minister must understand himself; Mr Brown has a risk-averse personality. An early election could have been too big a risk for him; he should have realised that from the beginning.

Mr Brown has also handled the Lisbon treaty as badly as he possibly could. He allowed Tony Blair to negotiate the treaty - with too little attention to the detail of British interest - and to sign it at the last European meeting before his retirement.

Mr Brown then failed to sign with the other European prime ministers, and refused a referendum on the grounds that Lisbon was not a constitutional treaty. This pretext has not satisfied public opinion, whichever point of view one takes. Mr Brown looks, at best, untrustworthy on European issues.

This combination of economic downturn, indecision and Europe has undermined his standing in the country. The latest opinion poll, taken by BPIX for The Mail on Sunday, must be the worst that any prime minister has had since polling began in the early 1940s.

The party preferences are bad enough. The Conservatives have 49 per cent with Labour on 26 and the Liberal Democrats on 14.

The personal ratings are even worse: 85 per cent think Gordon Brown is doing worse than expected; 44 per cent think he should quit now; one in three voters regards David Cameron as “attractive” but only one in a 100 finds Mr Brown “attractive”; by four to one, voters think that Mr Cameron rather than Brown represents change; 53 per cent wish that Tony Blair was still Prime Minister.

Public opinion often exaggerates. Mr Brown was not as good a Chancellor as the public thought, and he is not as bad a Prime Minister. Yet one cannot see how he can expect to win a general election in 2010. An added difficulty is that Labour is more or less insolvent, owing £24 million. I suppose Tony Blair might come back if Labour asked him nicely. Who would not prefer to live in Downing Street than Connaught Square?

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