Terrorists know how to capture the headlines. The killing of three British soldiers in Iraq and the massive car bomb intended to kill many in Central London were timed to challenge Gordon Brown and intimidate Londoners almost two years after the atrocities of July 7. The bomb is certainly a chilling reminder that the terrorist threat is as serious as ever. Relief that the car was disarmed before it was detonated must be tempered by enormous concern that the police and security services appear to have had no inkling of this latest attack, that terrorists are still able to smuggle deadly explosives into the centre of London and that they are still intent on killing and maiming as many innocent people as possible.

The first obvious response must be to underline to everyone – police, security guards and the public – the importance of vigilance. It was only thanks to the suspicions of a nearby ambulance crew that police were called to the suspect car. Londoners have become inured to the regular warnings on public transport, and are often blasé about the need for inspections and security checks. Inasmuch as Britons and tourists are determined not to let terrorists cow them, this is welcome. But it should not blunt the Government’s message, repeated yesterday, that Britain faces a “serious and sustained threat” from international terrorism.

To rely simply on policing, intelligence and public cooperation is not enough. The Government must look again at the legal failings that have thwarted attempts to tighten restrictions on those who would commit atrocities and have proved powerless against the determination of al-Qaeda to establish a foothold in this country. The new Home Secretary should look again at security legislation, in particular the absurdity that prevents police taking fingerprints or DNA samples from terrorism suspects held under control orders.

Police should be allowed to seize the passports of those suspected of heading abroad for terrorism purposes, and courts should seize the assets of those convicted of terrorism when it is believed that they may commit further terrorist offences. The Government should revisit the vexed issue of the time that a terrorist suspect can be held: both John Reid, the former Home Secretary, and the police back an extension beyond the current 28 days, and Mr Brown should lend his weight to seeking cross-party consensus. The Government must also overrule the quibbling by the security services and insist on the admissibility of telephone tap evidence in court. At a time when all electronic surveillance is increasingly important, it makes little sense to exclude potential vital evidence obtained from telephone intercepts.

The greatest failing, however, has been the appalling confusion over control orders. The latest fiasco is the disappearance of a seventh terrorist suspect, as embarrassing as it is damning of a system that is proving unworkable. It is time the Government admitted that all the compromises forced on it by the provisions in the European Human Rights Convention are inadequate. The legislation, which forbids the return of any suspect to a place where he might face ill-treatment and does not allow any derogation from this clause, is unfit for purpose. Drawn up in another age, it must be replaced by a convention framed for an era of terrorism. In President Sarkozy, Mr Brown would find a willing partner in a push for reform. Those who would kill and maim the people who offer them shelter deserve no protection.