A FEW WEEKS AGO I had the surreal experience of trying to stop the traffic in Hyde Park by holding one end of a police tape, while a nice but harassed policewoman tried in vain to stretch the other end round a lamp post. The tape was too short, and the drivers ignored us. It was the wrong day for a national emergency, as it turned out, but some of her fellow coppers were in a panic. One was screaming at three-year-olds to get off their tricycles, which was inevitably counter-productive. Another was swearing at bemused tourists to pick up their picnics as he cordoned off a huge swath of the park. Some bigwig had decided that a suitcase abandoned near Bayswater Road might be a bomb linked to the nearby Chechen memorial service. A fraught judgment to make, undoubtedly, and a tough job to do. But this was the British police as I have never seen them before: frightened, frightening and openly resented by the public. Is that really where the events of July have left us?

We are in a new place since July 7, our leaders tell us. The game has changed. Well, Bin Laden rolled the dice years ago, when he attacked America on African and Middle Eastern soil, while Britain kept its doors wide open to malcontents. New shards and splinter groups followed the pinnacle of horror that was September 11, 2001. July 7 was our Madrid, our Istanbul, our Bali. Finally the game came to us, and London was lucky that there were not more casualties. The enemy is fearsome, nihilist and bent on mass destruction, but it is not as if we have only just woken up to it. Scotland Yard had already foiled several plots when Sir Ian Blair, the Metropolitan Police Commissioner, said earlier this year that he did not regard a successful attack on London as inevitable. If the 7/7 and 21/7 attacks were linked, as the police now suspect, this could imply the existence of a sophisticated and widespread organisation. Or it may mean that the threat is more limited than we had thought. By themselves, it is hard to see that the events of July justify the haste with which the Government is rushing to prolong the suspension of habeas corpus.

If this particular evil breeds in the cracks of civilisation, then a proportionate response is even more vital. Fear can easily corrode a society that believes in nothing in particular, when that society is confronted by people who believe in annihilation. Of course we must starve the terrorists of the oxygen they need to propound their message and plot to kill. But over- repressive legislation will create resentment and help the enemy to breathe.

This is not to belittle the enormous task facing a police force whose members risk their lives to protect us. One of their many difficulties is the fact that so many terror suspects hire the same lawyer or legal firm. This can delay proceedings considerably, because each client must meet his brief. Which may be intentional. The legal firm Arani & Co has openly urged Muslims to call them, not the cops, if trouble looms. Lawyers usually advise their clients to remain silent. So the chances of convincing one suspect to inform on others are limited, even if it would be in his own individual interest. Extending detention without charge would help to combat the delaying tactics, but it is clearly a blunt instrument when it comes to securing a confession.

The police desire for a new offence of “acts preparatory to terrorism” is also quite understandable. The acquittal of all but one of those accused in the “ricin plot” suggests that the ancient offence of “causing a public nuisance” may not have adequately reflected the gravity of the threat.

Yet the very act of making it easier to charge suspects at an early stage of plotting will also make it less necessary to hold people for longer without charge. The police argue that the current 14-day limit is often insufficient to establish a case, because trawling for evidence is time-consuming. It can take longer than two weeks to decode heavily encrypted computer files and to examine CCTV evidence. Indeed, the investigations into the events of July 7 and 21 yielded 80,000 videos of CCTV footage and 1,400 fingerprints at 160 suspected crime scenes.

The police make a plausible case for occasionally needing more than two weeks. But it is a huge leap from 14 days detention without trial to three full months. There will always be one more file to thumb through, one more reel of film to view. But there will also be one more lie that the suspect can invent, one more innocent person drawn into the net by an honest mistake, one more potential martyr.

It is perfectly natural for the police to want to extend their powers. That does not mean that politicians should blithely accept their every suggestion. The Governmment’s insistence that the 90-day law would rarely be used is about as reassuring as its similar claims about its vague religious hatred law. The Prime Minister’s statement yesterday, that “I don't agree that the police would simply bang up anybody they wanted to bang up”, is in the same blokeish vein as Lord Falconer of Thoroton’s claim to the BBC a few months ago that “we know who we want to target” by outlawing the “glorification” of terrorism. But you cannot target legislation at people: this is part of the new Orwellianism.

If the Prime Minister is really determined to push through 90-day detention, he should make clear that any extension beyond the current 14 days should be viewed as extraordinary. The way to demonstrate that would be to allow High Court judges, rather than district judges, to conduct the weekly review of the case. Mr Blair may well feel that this would take him back to square one, by handing power back to the activist judges who have made his life so difficult over deportations. The irony is that their refusal to do the Government’s bidding on those issues makes them ideal candidates for this one.

Perhaps Mr Blair may yet amend his own Human Rights Act and think better of being too cavalier with age-old traditions of fairness. For we must all imagine what it might be like to be at the wrong end of the law. The police are in charge of security, and heroically so; but the politicians need to strike the right balance between security and liberty.

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