Only rarely does a proposal on legal reform win the support of such diverse organisations as the Conservative Party, the civil liberties group Liberty, legal experts and government ministers. The Prime Minister's announcement that he accepts the findings of the seven-month Chilcot Review, and is “minded” to allow phone-taps and intercepts to be used as evidence in court, is likely, therefore, to lead to a swift and welcome change that would bring British legal practice in line with almost every other Western country. It is a change for which this newspaper has long called, to overcome the anomalies that have arisen, especially in the prosecution of terrorist cases, and the unnecessary obstacles that have made convictions more difficult. Had intercept evidence been permissible in court, the outcome of the Omagh bombing investigation might have been very different; nor, perhaps, would the Government have been forced to tie itself in legal knots to detain a handful of foreign terrorist suspects in Belmarsh prison indefinitely and without trial.

Chilcot makes four points that are incontrovertible: there is an overriding imperative to safeguard national security; all trials must be procedurally fair; the State should, whenever possible, prosecute those it believes are involved in terrorism or other serious crimes; and in any criminal prosecution the best available evidence should be made available to the court. One objection to using the evidence of intercepts is that tapes or covert surveillance could be doctored. This is hardly compelling, and in any case the evidence, like any other, must be tested in court. Of much greater significance is the adamant opposition of the security services and police, which insist that the use of intercepts would reveal details of surveillance operations and techniques.

This objection must be taken seriously. Mr Brown told the Commons that “further extensive work” must be done to protect intelligence sources. But this could be done in many ways. Although defence counsels could demand to know how evidence was gathered, a judge could rule that any such disclosure should be made in camera. There is, moreover, no obligation on the intelligence agencies to transcribe material beyond a standard of detail deemed necessary. Nor should they be compelled to give up control over whether their material is used in prosecutions.

If, however, the police or MI5 overhear the details of a terrorist atrocity being planned, it is absurd that such vital intelligence can be used only to thwart an operation, and that the police must then look for other “admissible” evidence if they wish to bring a prosecution. This could take a long time - one reason why ministers want to extend detention of terror suspects beyond 28 days. Such an extension may often not be necessary if the intercept evidence can be produced.

At present, anomalies on the use and scale of phone intercepts abound. It is, however, pure coincidence that Chilcot comes at the same time as the row over the bugging of MPs and prisoners, which is a wholly separate matter. GCHQ, the government listening agency, argued that no change would pass the test of doing more good than harm. Clearly, it will find it harder and more costly to keep its interceptions covert. But continuing to give intelligence agencies a veto would delay indefinitely a change that makes it easier to prosecute the most dangerous terrorists and keep them away from society for years. That is how Britain can be best protected and why Chilcot is clear, compelling and right.