LONDON — It's hard to tell which was more impressive: the fall of the British Empire or the stiffness of the British upper lip as the empire crumbled away. Between the two world wars and during most of the Cold War, a serenely united British establishment made one disastrous foreign and economic policy decision after another until, by the late 1970s, the most dynamic, advanced and powerful society on Earth had become little more than a moth-eaten tourist attraction. An old New Yorker cartoon neatly captured this serene, inexorable decline. Two pith-helmeted Britons have sunk impassively up to their necks in jungle muck. Says one: "Quicksand or not, Quigley, I've half a mind to struggle."

But lately, the British have indeed started to struggle, and the country's long decline has stopped as both the British right and left have recovered their vigor. First Margaret Thatcher's free-market enthusiasm drove the left into paroxysms of rage; then Tony Blair smashed the socialist wing of the British Labor Party and forged an extraordinary, unlikely partnership with President Bush that divided Europe and enraged the British political world. Now Ken Livingstone, an unreconstructed left-winger nicknamed Red Ken who was once purged from Blair's party, is mayor of London as that city pushes past New York to become the capital of global finance once again. Another Labor expellee, the flamboyant member of Parliament George "Gorgeous George" Galloway, supported Saddam Hussein in 2003, faced down a sputtering U.S. Senate committee, then appeared in red spandex on a reality television show.

British politics are boring no longer. Neither is British life.

The newly galvanized Britain isn't always pretty or safe; change never is. Radical Muslims continue to fan the flames of terrorism in the nation's divided, multiracial cities, while more moderate Muslim immigrants debate whether and how to integrate into the larger society. Sunday afternoon in Hyde Park's famous Speakers' Corner now features Christian and Muslim evangelists and apologists waving holy books and citing texts as they harangue one another about fine doctrinal points.

Meanwhile, the old class system is breaking down as investment banks bring world-class talent to London. Hundreds of thousands of immigrants from across the European Union are also being drawn to Britain's more open economy. Earlier this year, the Times of London reported that the name Muhammad is second only to Jack as the most popular for baby boys in Britain — and is likely to rise to No. 1 next year. In many ways, London is now a more international city than New York; talented young people from all over the world are incubating new ideas and new values in a city that is more exciting than at any time in living memory.

A recent survey found that as many as two-thirds of the jobs created by Britain's Labor government have gone to immigrants from the European Union and elsewhere; this was cold comfort to the suddenly shaky new government of Prime Minister Gordon Brown, but it points at the newfound dynamism of British life — and its attractions for talented people worldwide.

Even the food is improving. As an 11-year-old boy in an English school, I was not only caned (a punishment now banned by the European Union as a human rights violation), but every day I confronted some of the blandest, mushiest and most overcooked grub in the Western world. British schoolchildren now get menus vetted by celebrity chefs, and new generations of South Asian, Middle Eastern and European entrepreneurs and cooks have turned London into a destination for foodies. It's still easy to get bad, overpriced food in Britain, but some of the world's best restaurants have sprung up to serve the investment bankers and plutocrats now swanking through the London streets.

This doesn't mean that the British are happy. Far from it. The Age of Bush has seen Britain plumb new depths of self-loathing. Texan, self-confident to the point of arrogance, loudly Christian, optimistic, unembarrassed by the use of power: Bush represents everything American that Britain hates. Britons left and right writhe with anger and embarrassment over what they view as their country's hideously inglorious role in the Iraq war: poodles of the unspeakable Bush.

They need to cheer up. Something strange and different is taking shape in the land of the crumpet and scone. Indeed, I feel a little like Paul Revere: The British are coming — or at least coming back.

If so, watch out. Remember, this is the birthplace of parliamentary government, modern finance, the Industrial Revolution and the basic concepts of free-market economic thought. At its peak 90 years ago, when victory over Germany and the Ottoman Empire allowed it to increase its Middle Eastern and African empires one last time, Britain ruled about a quarter of the world's land and a quarter of its population.

While skeptics sniff that the British recovery under Thatcher and Blair was what Wall Street calls a "dead-cat bounce," something much more important seems to be under way. The British are doing a better job than the Americans at managing their financial system. New U.S. accounting and reporting requirements in the aftermath of the Enron debacle strike many international investors as cumbersome and intrusive, and the subprime mortgage crash has shaken global confidence in American finance. Add to this the troubling decline of the dollar, and the British financial system looks better managed, more private and safer than the leading alternatives.

Britain's role in Europe also seems to be evolving. For 200 years, the nation played a balance-of-power game, protecting Europe's weaker states from its stronger ones. But after the Cold War, with a powerful Franco-German alliance dominating the continent, Britain found itself marginalized in European politics. That has started to change: The new members of the European Union in Central and Eastern Europe see Britain as an ally, and the Paris-Berlin axis is steadily weakening.

Perhaps most important is Britain's new cultural and political turbulence. Back when Britain was great, its people disagreed and fought all the time. This dynamic society was like the world's Goldilocks; its conflicts weren't hot enough to create cataclysms like the Russian and French revolutions, but it wasn't as cold and immobile as the tradition-bound societies that failed to adapt to changing ideas and technologies.

The result? In politics, culture and science, Britain is on the upswing. Thatcher and Blair both created models of political economy — sometimes vilified and sometimes praised — that have influenced countries worldwide. Meanwhile, figures such as the portrait artist Lucian Freud and the shark-embalming Damien Hirst have put London at the cutting edge of the visual arts; London's theater scene is the most vibrant in the world — except during the Edinburgh International Festival. And only the United States has racked up more Nobel Prizes in science than the United Kingdom in the past 10 years.

Britain will not rebuild its empire or rule the waves once more. The days of British governors and viceroys are, thankfully, over. But Britain, the country that did more than any other to shape the world system in which we still live, is warming up for an encore. Unlikely as it may seem, Britain is once again a rising power. Just as prime ministers such as Thatcher and Blair loomed larger on the world stage than the hapless James Callaghan and Edward Heath (remember them, anyone?), future British prime ministers will loom larger still.

Keep your eye on the steeple of the Old North Church.

Walter Russell Mead is a senior fellow at the Council on Foreign Relations. His most recent book is "God and Gold: Britain, America and the Making of the Modern World."