In the person of the queen, Elizabeth II, the best of British tradition has been on display in America over the past few days — a reminder, necessary in these times, of the enduring values that still unite the English-speaking peoples. Yet even as we thrill to this spectacle a pillar of that relationship is about to be removed. After ten years in office, Tony Blair will finally announce his resignation. The man who has been America’s staunchest ally in war and peace will be gone.

What lies in store for Britain in the post-Blair era — and what does his departure mean for America? At home, Mr. Blair’s achievement is considerable. He has presided over a decade of prosperity and stability — the first Labor prime minister to do so. By European standards, Britain is still a good place to do business. Blairism has left the entrepreneurial framework of Thatcherism largely intact.

But the tribute paid by productive citizens to Labor’s leviathan has been high. The welfare state, with all its malign consequences for public and private morality, is out of control. The pension system is heading for bankruptcy. The bureaucracy that still runs health, education, and other public services resists reform.

Though Scotland, Wales, and Northern Ireland still expect to be subsidized by London, central government is resented at the periphery. Despite Mr. Blair’s policy of devolution, the United Kingdom looks increasingly fissiparous. In Scottish Parliament elections last week Nationalists ousted the Labor Party for the first time in half a century on a platform of independence for Scotland.

Unfortunately for Mr. Blair, his anointed successor, Gordon Brown, has, as custodian of the Treasury, been chiefly responsible for the growth of taxes and spending since 1997. Mr. Blair has tried to stop Mr. Brown, whom he sees as being in thrall to Labor’s socialist instincts, taking over. Incredibly, not one of Mr. Blair’s disciples has had the gumption to challenge Mr. Brown with an alternative to his big government agenda.

The culture of dependency has begun to corrupt even the commercial and professional classes, who now look to government to set the world to rights. This addiction to state intervention goes hand in hand with an aversion to the only proper justification for such intervention — the defense of national security. Even the Tory leader, David Cameron, recently declared that the great issues facing his country were: globalization, global poverty, and global warming. Mark that global jihad fails to feature.

It is here that Mr. Blair will be most painfully missed. He, at least, has been consistently and courageously right about the war on terror. Yet despite his brilliance as an advocate of Western civilization — a skill that we hope will be put to good use in the next phase of his career — he has not persuaded his own countrymen that the war in Iraq is still winnable and must indeed be won if Al Qaeda is to be defeated.

Mr. Brown, whose unpopularity is equalled only by his unintelligibility, is widely expected to accelerate the withdrawal of British troops from Iraq and may even scale down their presence in Afghanistan. Nothing in his record so far suggests that Mr. Brown grasps the need to expand and improve the British armed services, which are unequal to their task as America’s principal ally.

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From America’s point of view, however, Mr. Brown faces an even more serious challenge: to stop the transformation of his own back yard into Al Qaeda’s happy hunting ground. At a minimum, the Bush administration will expect him to cut off the two-way traffic between British inner cities and terrorist training camps in Pakistan. The present U.S.-U.K. visa regime, which is liberal, is unsustainable unless Britain ceases to be a major exporter of terrorists.

Though Mr. Brown prefers Democrats to Republicans, he is genuinely pro-American. With Chancellor Merkel and now Nicolas Sarkozy as partners, he is more fortunate in the European company he will keep than Mr. Blair was with Gerhard Schroeder and Jacques Chirac.

That is just as well, because there is a real danger that Britain without Mr. Blair will be more like the rest of Europe in its attitude not only to America but crucially also to Iran. If Mr. Bush or his successor decides that military action is necessary to stop Iran from carrying out its threat to wipe Israel off the map, will Britain come down on America’s side or Europe’s?