This time we were lucky. This time . . .

The historic aims of terrorism are to disrupt society and to radicalise the community to which the terrorists belong. A terrorist campaign that reaches the scale of that in Iraq, or one that is concentrated on a key target such as the twin towers, can cause significant disruption. The terrorists of Baghdad have wrecked the economy of Iraq and caused widespread havoc in a campaign employing high levels of technical efficiency. In terms of technical aid to terrorists, Iran has a lot to answer for.

But a smaller-scale campaign can still reach the terrorists’ other objective of radicalising their own people. The IRA achieved this in Northern Ireland, though not in the rest of the United Kingdom. Communities can become radicalised if the security response seems to be hostile to the whole community, or if they are subject to the anger of other communities. In Britain we need to consider the responses of other minority communities to Islamist terrorism, as well as the reaction of the host community at large.

The car bombers in London and Glasgow were not technically efficient. In the early years of Irish terrorism there were similar events, in which the terrorists missed their targets, or blew themselves up. These failures resulted largely from lack of experience in handling explosives. There will usually be a race between the rising efficiency of the terrorists and the competing efficiency of the security services.

Last week the terrorists did manage to reach their targets of London nightclubs and Glasgow airport, but they failed to detonate the fire storms they had intended. If they had done so there may have been very heavy casualties, and the public response might be much more extreme. There were hundreds of people in the Haymarket nightclub.

In Britain the security services have a strong recent record. If one had been asked in September 2001, which is now nearly six years ago, how many terrorist casualties or terrorist attacks Britain would have to suffer in the following six years, one would probably have guessed at much higher figures. Good intelligence work has undoubtedly thwarted a considerable number of plots. It is probably true that the response to the IRA brought our antiterrorist systems to a high level of efficiency.

Nevertheless, there will be further terrorist attacks on Britain, and some of them are likely to succeed. This time the terrorists reached their targets without detection. In all probability, they will do so again – and next time their bombs will, very probably, function as intended. There is only one reasonable assumption on which to base government policy. We face a long-term terrorist campaign against Britain, which may last for years; the organisation and training of the terrorists will improve. The danger will become greater.

This may be a campaign of occasional, spectacular events, on the lines of al-Qaeda, but there are also likely to be more frequent attacks on vulnerable targets. This may require changes in the law and increased resources for the security services. Admittedly there has been too much hasty legislation since 9/11 – the Extradition Act 2003 is an example of lopsided lawmaking. We do not want to have any more of that. Yet there still seem to be gaps in our legal system for dealing with terrorism. The best legal approach would be to make it easier to convict terrorists on solid evidence under the existing criminal law.

The Conservatives have offered to cooperate with the Government if it wants to amend the law on using phone-tap evidence. Most other countries do allow the admission of such evidence; it is better to convict alleged terrorists on this evidence than it is to keep them under the inadequate supervision of control orders. Beyond that, it might be a good idea for the Government and Opposition to establish a joint committee to consider other desirable changes in the laws on terrorism.

One of the biggest problems for any terrorist organisation is the risk of being penetrated by the intelligence services. There is the story of a Bolshevik cell before the First World War in which every member turned out to have been an agent of the Tsarist Secret Police. Undoubtedly there were many such informants inside the IRA. The successful penetration of a terrorist group depends on organisation and money, which the Government will have to provide. However, it also depends on the attitudes of the community from which the terrorists come.

Many Muslims have been alienated from British society by the Iraq war and by public hostility based on the fear that they may be sympathetic to Islamic terrorists. But there are also many Muslims who think terrorism is evil, who are not fundamentalists, who want to create a satisfactory life here. They may well be reluctant to report the nice young man down the road who may, or may not, have joined a terrorist group, but they would be horrified to think that one of their own children could become a bomber.

Terrorism is, inevitably, a running battle of intrigue and intelligence, of recruitment and penetration on both sides. Yet it is always a cultural struggle, a Kulturkampf in Bismarck’s terms. The terrorist seeks to destroy our cultural life, yet our culture has itself a seductive appeal to those who might otherwise become terrorists. Many Muslims resent what they regard as injustices to Islam, but few of them support the massacre of the innocent; most of them want to enjoy the pluralist opportunities of modern Britain.

A cultural struggle can be shaped by technology, as Karl Marx observed, but history does not suggest that it is often decided by technology. Bismarck had the guns, but he lost his struggle against the German Catholic church. Our own culture is deeply flawed; that is what makes us so vulnerable.

William Rees-Mogg