The struggle against Islamist terrorism will probably extend for decades, and what might have been designed as emergency measures need to last. So we need to find a way for a protective State not to become an intrusive one, a way to keep the public on side. A fascinating approach to the problem comes in a new book called The New Protective State, edited by the historian Peter Hennessy.

It makes the case for an ethical basis for intelligence work just as there are ethical criteria for war: to defend the institutions of a free society, to limit the dangers of restrictions on individual liberty and maintain public confidence.

One proposition is based on the experience of Denmark’s intelligence service, which produces for public consumption an unclassified version of its annual assessment of threats. If the exercise were copied in the UK, then the experience of the British government “dossiers” before the Iraq war might make it hard for the public to trust such an annual intelligence report. But that may come, provided that it was clear who wrote the report and who authorised it.

It would explain to the public the grounds for security policy while distinguishing between political and intelligence judgments. There is also a need for a proper process of authorisation for the gathering of sensitive intelligence, and judicial scrutiny of the activities of the intelligence services.

Gathering intelligence against a loose network of terrorists is different from the intelligence practised in the Cold War. Accurately assessing military capabilities and intentions was integral to denying advantage to the Soviet Union. While the consequence of a miscalculation might have been the destruction of civilisation, the identity and location of the threat were obvious. This is not true with small theocratic terrorist groups, who might kill thousands of civilians but who do not currently represent an existential threat. This inevitably requires a high degree of domestic surveillance.

This is why fresh thinking about a new protective State is necessary. Some sacrifice of privacy is necessary, but – because the threat will be with us for a long time – it needs to be made formal rather than being an unplanned and insidous encroachment on civil liberties.

For those of us who see the struggle against theocratic fanaticism as the antitotalitarianism of our time, there are some principles that cannot be breached: a prohibition on torture at one extreme, and on a more mundane level that the security services are made accountable to outside bodies.

It will be a long struggle; but as we learnt in the Cold War, a liberal society with free institutions is more adaptable than anything available to our totalitarian enemies.

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