They produce quantities of fine words written to be forgotten and innumerable promises made to be broken. History says that replacing the G8 with the G20 is no more than a gesture designed to spread the inevitable blame a little more widely.

From Pittsburgh, nevertheless, comes the sound of heroic optimists talking of a new world order. The fate of the last of those – the older Bush, the “peace dividend”, battle tanks into ploughshares, and justice for all? – is forgotten. This time, things are different.

They are, too, though whether there is a choice involved, for the west at least, is another matter. Formal recognition for the world’s emerging economies, with China and India at their head, was inevitable even before the banking crisis. That smash has concentrated minds as it has emptied purses. The primary relationship – between US consumers and Chinese workers – has shifted power, and shifted it permanently.

Consequences follow, and not just within the Group of 20. The IMF’s voting arrangements will change, for example, to reflect the new reality. Why should the French, to take one example, have twice as much clout as the Chinese in the affairs of the fund? Because China is not a “mature democracy”? Why – and this is America talking – should Britain and France, rather than Europe, have seats on the IMF board?

The tremors spread. President Barack Obama tries to set the United Nations back on the road to nuclear non-proliferation and dares to speak seriously of disarmament. Our Gordon Brown – granted the honour of a brief meeting in a kitchen – chips in a nuclear boat. This is encouraging stuff. But where does it leave Britain’s claim to a permanent seat on the security council? Where does an upheaval in world affairs leave Britain generally?

A cynical view: vastly indebted and tripping along beside a vastly indebted US while the dollar’s days as a reserve currency begin to be numbered. Tripping along, meanwhile, as trappings are stripped away – UN, IMF, “special relationship” – and a new global architecture emerges.

Now wonder: is that really such a bad thing?

It must provide bitter amusement to those outside America’s orbit, for one example, to see so much time being expended in Pittsburgh on bankers and their rewards. A workable strategy – believe it when you see it happen – is certainly important. But why should any of the emerging economies, far less the permanently distressed countries of Africa, welcome any attempt to patch up the so-called Washington model to which Mr Brown subscribed for so long? It took the world to hell in a turbo-charged handcart.

The financial crash, like the G20 realignment, confirmed every suspicion. American leadership had become, in that modish word, unsustainable. Hence President Obama’s attempts this week to dig his country out of a mess, if his country’s introverted Congress will allow him.

The insane missile “shield” will go. The environmental crisis will be acknowledged (and confronted?). Non-proliferation – cost-effective, congenial to Russia, and an answer to Iran’s games – will be taken seriously. And American capitalism, with its British sidekick, will acquire humility. In that regard, there is no choice.

An HSBC report this week was one straw in the wind. It argues that those countries claiming their places at the G20 cannot tolerate western interest rate policies for much longer. With the US and Britain contemplating debt at 100% of GDP, global “rebalancing” becomes a matter of when, not if, and that, as the oil runs out, means an end to the dollar’s pre-eminence. The currency, as the bank’s David Bloom has put it, “looks awfully like sterling after the First World War”.

None of this means that the world will be a better place. China, as our politicians sometimes remember, is no champion of liberal values. But to state the fact is akin to saying that the UN is invariably useless, that the G8 was riddled with hypocrisy, that the IMF is more often the problem than the solution. What’s the alternative? Cold war between China and the US? Overt economic piracy as the devil takes, and he will, the hindmost?

You can pick an illustration at will. Many of us would be rid of all the Trident boats, but only one of us is Gordon Brown. A real attempt to curb bankers would earn you a vote to shame Stalin, but it will only happen with international governmental co-operation.

Iran’s decision to confess to the existence of a second enrichment plant (so much for western intelligence) is a case in point. America cannot solve this proliferation problem. America allied with Europe has failed to find a solution. But Obama now has Russia on board, so it appears, while China stalls over sanctions. The process is less than elegant, it is tainted by naked self-interest, but it beats known alternatives.

So with the G20. It was always absurd to believe and behave as though seven countries, with Russia on the guest list, could presume to shape the world’s affairs like some deluded board of directors. Unjust was one word for it. But while you could hardly claim that the likes of China, Saudi Arabia or Turkey will contribute to the onward march of democracy, their right to membership of the remodelled forum is undeniable.

Yet is that a new world order? If rights are the issue, why stop at a G20? The IMF has 186 members, all of them – the African nations not least – with pressing concerns. If it is true that trade and growth depend on the rule of law, and if law implies democracy, what hinders a G186? Something called the UN, no doubt. Ninety minutes from Gaddafi on appropriate rewards for bankers: any takers?

Beyond gruesome fantasy there is, for some, gruesome truth: the “rich” north has caved. Its stewardship of the world economy has been catastrophically costly. Meanwhile, “emerging” economies have emerged actually, to a greater or lesser degree. Money has talked, though not in English, and the end of the American

Century is in sight.

Obama’s domestic constituency will not like the sound of any of this. Chauvinism aside, they have a point. China has achieved capitalist ends by totalitarian means. That was never in the script. Economic growth was supposed to bring democracy and liberty in its wake, as though by magic. Now China and India are acknowledged as the peers of America and Europe. We will have to live with that.

Against the success of those newcomers, after all, can be set the failure of the incumbents, countries and alliances so nearly redundant they persist in confusing futile wars with global influence. Britain wins this worthless prize, and risks losing its diplomatic status symbols as a result. America has the hardware still, and the economic weight, but Obama has been explicit: the neo-con fantasy of a monopolar world, shaped by American capitalism, is over.

The bankers will still be rich after the dust has settled. As it turns out, it is easier for great powers to make ringing declarations over the nuclear threat or climate change than to curb a few wide boys. After all, as some of that crew have threatened, if things become uncongenial they can always decamp to Mumbai, and to the new world.