Matthew Norman: The quaking wretch in Downing Street

Many of us see the cash-for-honours case in the same light as the Feds getting Al Capone for tax evasion

His master across the seas lies paralysed on Pennsylvania Avenue from Tuesday's collision with the Democratic juggernaut, the mayhem continues to worsen in Afghanistan, and what might indulgently be termed his policy on Iraq is about to be obliterated by Rummy's successor at the Pentagon. And through all the chaos, the thing that preoccupies Mr Tony Blair to the exclusion of all else is where the Metropolitan Police will finally feel his sweat-drenched collar.

According to credible reports, our PM and his advisers are in "meltdown" over the investigation into the alleged flogging of peerages. It is no longer a matter of whether he will answer the questions of John Yates of the Yard, nor really of when. It will happen fairly soon, and the one important question (apart from whether it takes place under caution; and even that, considering Lord Levy was cautioned, seems inevitable) is geographical.

If the interview is held in his Commons office, as he must pray, there will be no pictures of Mr Yates arriving at all, while photographs of a large Rover gliding through the electric gates of Chequers won't have a fraction of the impact of the one that petrifies him. That, of course, is the picture on every front page and at the start of every television news bulletin of Assistant Commissioner Yates passing one of his constables as he enters No 10.

Tempting as it is to say that even Mr Blair couldn't last a month after that, idiots like me have predicted his imminent demise too often not to have learnt this truth: there is no embarrassment the man cannot stomach, however intense and seemingly intolerable, to cling to office. So while civilians and soldiers die in far-off lands of which he must wish we knew little, that quick but shallow dodgy lawyer's mind of his will be whirring away in the quest for a survivalist plan.

Perhaps he's already found one. According to one report, no charges will be lain until he has left his job, largely because his staff have been so lethargic in handing over documents that the Crown Prosecution Service won't be in a position to decide until next summer. Why Mr Yates couldn't impound every computer hard drive in Downing Street I'm not sure, but doubtless the traditional catch-all rebuttal to any invitation to government to disclose information - "national security" - would be involved.

While it rumbles on, cameo players expose the saga's richly surreal quality. The Met Commissioner, Sir Ian Blair, bafflingly cites his close working relationship with the PM as an excuse to play no part in the investigation - even though he wouldn't be involved in deciding whether to prosecute, and even though his namesake isn't in fact his boss.

Conversely, the Attorney General, Lord Goldsmith, declines formally to recuse himself, even though he has a central role in that decision, and even though Mr Blair is most certainly his boss. Such is the Alice in Wonderland reality in a country with no written constitution and no real concept of the separation of powers.

Over in Washington, meanwhile, the powers are now as separated as could be. For the first time in years, we can look enviously across the Atlantic at a political system with an inbuilt defence mechanism capable of punishing a rogue leader by shackling him to a hostile legislature.

As the next two years will illustrate, American democracy, for all its failings, remains a vibrant force for self-examination. There, a Democrat-dominated Congress will investigate the Iraqi casus belli to death, making his remaining time in the White House an abject misery for a president powerless to trot out the intelligence-insulting gibberish emanating from Mr Blair last week that any inquiry would undermine troop morale.

There, it would be unthinkable for an attorney general to take any part, even symbolic, in decisions relating to a possible criminal trial for the man who appointed him. Far from keeping Richard Nixon out of trouble over Watergate, after all, John Mitchell did time in prison himself. There, abuse of power for sexual gratification in the office led to impeachment proceedings, however laughable, against an incumbent president. Here, John Prescott was punished with the retention of his title and salary for a vastly reduced workload.

The insane statistical anomaly that permits a British PM absolute power over foreign and domestic policy with about one-third of the popular vote, and the support of a fifth of the electorate, is an argument for another day. It's the complete absence of any checks and balances against that unfettered power that is so starkly highlighted by the outcome of the midterm elections.

Or, rather, the near complete absence, because thankfully even a British prime minister is subject to the law, even if the specific law in question seems comparatively trivial. Many of us, I suspect, will see the cash-for-honours case as the equivalent of the Feds getting Al Capone for tax evasion, believing that the charges Mr Blair really ought to face relate not to selling black market ermine but to the commission of war crimes.

Who knows, perhaps when he's old and infirm like General Pinochet, Mr Blair will be seized from his bed and rendered by executive jet to The Hague. It sounds unlikely, but who'd have believed last year when John Yates began his investigation that it would lead to talk of paper trails and smoking guns, to fears that Michael "Squealer" Levy might tell the fuzz where the bodies are buried, and to "meltdown" in Downing Street?

Mr Yates cultivates the image of the plain copper, like one of those black and white B-movie pipe-smokers, quietly but relentlessly doing his job, and so perhaps he is. But he is a more influential figure than that. Already, through his dogged unconcern about offending the mighty, he has restored some confidence in police independence; and regardless of whether he is ever pictured at the door of No 10, already he has done to Mr Blair what American voters did to Mr Bush on Tuesday. He has thoroughly and publicly humiliated a vainglorious, religiously maniacal leader who believed himself above all earthly rules, great and small. Mr Yates is the equivalent of one of those Assyrian slaves who stood behind Roman emperors whispering, "You too shall die, Lord, you too shall die".

More even than that, he has reduced the Prime Minister to a quaking wretch, alone in the world with his guv'nor in Washington done for, skulking beneath his desk like the star of one of those 1960s public information films about how to survive a Soviet nuclear strike. The man's last role in government, it seems, is as living caution against the folly of trusting in the supremacy of one's own moral rectitude, and that's surely the most useful one he has ever played or ever will. What possible harm can there be in letting him stay there playing it for as long as he wants?