Bruce Anderson: Mr Blair's political conjuring tricks have finally lost their power to fool the public

Even in politics, funerals can be dignified events, but not if the corpse refuses to be buried

When Mr Cameron's closest advisers heard the details of the reshuffle, they rushed to reassure themselves. No, this was not 1 April, it was actually happening. Suddenly, the words amazement and incredulity seemed inadequate. If Tony Blair had allowed David Cameron to do the reshuffle for him, the Tory leader would not have dared to inflict so much damage on the Labour government.

If you are going to keep John Prescott in office, there is a case for stopping him doing anything. That is the only way to align his responsibilities with his abilities. But hard-pressed taxpayers are unlikely to be so philosophical. They have grasped the point that Mr Prescott has two Jags, two shags, two official residences, and a large salary - all for nothing. They might agree that it is better for John Prescott to be idle, which he can just about manage, than to try to act as a minister, which he would, as it were, cock up. They will not understand why he has to be paid for doing nothing.

Downing Street is now trying to hold the mockery and anger at bay by claiming that Mr Prescott will chair various committees: climate change has been mentioned. But surely it should have a chairman who could get within three syllables of pronouncing "science". John Prescott is doing his best to bring about climate change, political climate change.

From Mr Prescott, we move upwards to mediocrity. The foreign secretaryship is one of the hardest jobs in government. The ideal candidate should combine intellect, experience, judgement, gravitas and eloquence. He should also have a relationship of mutual respect with the Prime Minister so that he could accommodate the PM's desire to run foreign policy himself - they all do - while ensuring that the FO is not marginalised.

Margaret Beckett has none of those qualities. She is dull, drab, dim, and sullen. It has been assumed that there were two reasons for her longevity in Cabinet. First, her insignificance: no one remembered to sack her. Second, her insignificance: Mr Blair has always known that if he ever needed to create a cabinet vacancy, she was available. She had no political constituency, and no one would ever have said: "Poor Margaret, what a harsh way to treat someone of her talents." Margaret Beckett is surely the least able and least qualified Foreign Secretary of all time. I doubt if Luxembourg could produce a rival. She would be at full stretch as San Marino's minister for caravanning.

Though Jack Straw was not a great Foreign Secretary, he could do the work and a number of his officials insist that they respected him (I suspect that they are confusing respect with like). So why move him? It is true that some of President Bush's people were annoyed by his enthusiasm for ruling out military options in Iran. It is also true that no one has yet produced plausible military options, and that Mr Straw had a good relationship with Condi Rice.

When Mrs Beckett goes to Washington, she may have a better initial reception than she deserves, because she will remind people of Madeleine Albright. That will only work until she opens her mouth. Mrs Albright has a brain.

The Butler report criticised Mr Blair for sofa government: running foreign policy from Downing Street with no strategic planning or even minutes. We now know how much notice Mr Blair has taken of Lord Butler: none. You are bound to continue with sofa government once you choose a Foreign Secretary who is less intelligent than the sofa.

Mrs Beckett will have the assistance of Geoff Hoon. It is a sign of Mr Blair's diminished competence that Mr Hoon left Downing Street unaware that he had been demoted from the Cabinet. It is a sign of Mr Blair's diminished authority that Geoff Hoon did not hesitate to vent his feelings in the press.

One can sympathise with Mr Hoon. If you are going to be part of a pantomime horse, it is better to be the front end. There is also a Eurosceptic reason for welcoming the Hoon appointment. If Mr Blair had any plans to revive his European agenda, he would surely have chosen a less ineffective minister. That said, Geoff Hoon is hardly the man to resist the relentless pressure of Euro-encroachment. It would help to have a minister who would fight for British interests with a tenth of the energy that John Prescott deployed in fighting for his perquisites. That is not Geoff Hoon.

Nor is John Prescott the only minister desperate to keep the perks, even though the power has gone. How else could Tony Blair be described? With every passing hour, he seems to find a new way of becoming more tawdry, more diminished. Even in politics, funerals can be dignified affairs, but not if the corpse refuses to be buried and insists on decomposing in public.

At least since the war, there has been an iron law of British politics. All governments that lost office had already died in office. The voters who turned them out were merely ratifying their loss of power. That was true in 1951, 1964, 1970, 1974, 1979, and 1997. On present indications, it will also be true at the next election.

No wonder so many Labour MPs are in revolt. If it were as easy to mount a challenge to Blair as it was to Tory leaders in Mrs Thatcher's day, the stalking horse would already be gathering names. In the Labour Party, the thresholds are higher, but the names are accumulating, while Gordon Brown is furiously brooding. He is trying to answer three questions: could Tony Blair be persuaded to go quickly and voluntarily? If he refused, could a lesser figure precipitate a leadership contest to open the way for Mr Brown without wrecking the Government. If the answer to that were no, could Mr Brown himself force a change without wrecking the Government?

Although it is not yet clear how and when Mr Brown will answer those questions, one point is clear. There can be no recovery for Tony Blair. In one respect, he is still the most formidable politician in Britain. Because he can always persuade himself that what he is saying is true, he has not yet lost his conjuring skills and is still able to mesmerise interviewers. But it is all a trick, as is becoming more and more apparent to more and more people.

Mr Blair has slipped below the threshold of credibility and there is no way back. The Prime Minister himself does not accept this. He seems convinced that he is indispensable, that there is still time for him to win a great legacy and a place in history, and that he is the only man who can lead the Government. In the course of Friday's reshuffle, some strange ministers were given some stranger titles. Who knows? There might even be a minister for delusion, reinforced by a cabinet committee, chaired by John Prescott. If so, the Department of Delusion ought to take a close interest in No 10 Downing Street.