There is no less threatening figure of authority than the British police officer. He or she is normally unarmed, incorruptible, and polite. That is, at least, the ideal that the world has always cherished.

A German-Jewish émigré once told me of how, as a youth during World War II, he had joined the audience at Speaker’s Corner in London’s Hyde Park, where, by tradition, anybody may say what he likes. To his astonishment, the policemen were there, not to arrest or even spy on the soapbox orators, but to protect their freedom of speech. These were not the kind of policemen he had known in his native Germany.

Today, however, it is rare to encounter these paragons, except at high speed in a patrol car. The most law-abiding country in the world has lost much of its respect for the law and its guardians. Now, as his parting shot, Tony Blair has promised to give the police new powers that they have not enjoyed since 1945.

At present, British police have the right to stop and search anybody they deem suspicious, but not to demand that they reveal their identity or movements. In the future, a police officer will be allowed to ask who you are, where you have been, and where you are going. Those who refuse to answer may be charged with a criminal offense and fined up to $10,000.

It is scarcely necessary to explain to American readers that the justification for these new police powers, hitherto unheard of except in wartime, is the War on Terror. But it is by no means certain that Parliament will grant these powers or that the courts will uphold them.

The legislative and judicial branches of government have combined to constrain the executive branch in its efforts to prevent the spread of radical Islam. The courts have decreed that foreigners suspected of preaching or participating in terrorism cannot be deported. Mr. Blair’s own party combined with his opponents, though, want to cut down the time that suspects could be interrogated before being charged to just 28 days from 90.

Most notoriously, three years ago the indefinite detention of foreign suspects without trial was ruled illegal by the law lords — the equivalent of the Supreme Court. In a notorious judgement, Lord Hoffmann declared: “The real threat to the life of the nation, in the sense of a people living in accordance with its traditional laws and political values, comes not from terrorism but from laws such as these.”

Instead of keeping such suspects under lock and key, the government has been forced to impose a much weaker form of surveillance: the “control order.” This means that suspects can be ordered to report to a police station regularly if there is insufficient evidence to bring them to trial.

The unintended but predictable consequence of depriving the police of the powers they need became plain last week when it emerged that three terrorist suspects under control orders had absconded. They, like others who have evaded justice, may already be abroad, perhaps fighting British or American troops in Iraq.

An article by the prime minister in this week’s Sunday Times reads like a cry of frustration: “Over the past five or six years, we have decided as a country that except in the most limited of ways, the threat to our public safety does not justify changing radically the legal basis on which we confront this extremism. Their right to traditional civil liberties comes first.”

He goes on to say: “I believe this is a dangerous misjudgment. … This extremism can be defeated. But it will be defeated only by recognizing that we have not created it; it cannot be negotiated with; pandering to its sense of grievance will only encourage it; and only by confronting it, the methods and the ideas, will we win.”

Mr. Blair is right and the human rights lobby is wrong. We need the police to have the powers they need, not merely to bring terrorists to justice after they have committed an atrocity, but to prevent them from committing it in the first place.

So the British bobby on the beat really does need to be a little more inquisitive when questioning members of the public. I feel confident that American visitors in London, whether on business or vacation, will find the police as courteous as before.

But the new powers are of no use if the police do not use them. The test of the new government of Gordon Brown will not be whether it is prepared to temporarily suspend the civil liberties of society in general. No: its mettle will be measured by its readiness to confront Muslims in Britain.

If the police single out a Muslim for questioning, or if they need to search a mosque, or if they appeal for information about a terrorist on the run, they should not expect a barrage of complaints about Islamophobia and discrimination, but patient cooperation. Will they get it?