Ken Macdonald: We must not degrade our liberties in the name of defending them

We need to take very great care not to fall into a way of life in which freedom's back is broken by the relentless pressure of a security state.

We need to understand that it is in the nature of state power that decisions taken in the next few months and years about how the state may use these powers, and to what extent, are likely to be irreversible. They will be with us forever. And they in turn will be built upon. We should imagine the world we are creating before we build it. We might end up living with something we can't bear.

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Of course our country faces very significant risks. And I have enormous admiration for all those who work with such energy and verve to combat those risks. The prosecutors in my Counter Terrorism Division have similarly distinguished themselves. Their efforts have been absolutely grounded in due process and pursued with full respect for our historical norms and for our liberal constitution.

This has worked. Our conviction rate is in excess of 90 per cent – unmatched in the fair trial world. We have a guilty plea rate of over 40 per cent. So we have been absolutely right to resist special courts, vetted judges and all the other paraphernalia of paranoia.

Of course, you can have the Guantanamo model. You can have the model which says that we cannot afford to give people rights, that rights are too expensive because of the nature of the threats. Or you can say, that our rights are priceless. That the best way to face down those threats is to strengthen our institutions, not degrade them.

It is difficult to see who will maintain a cool head if governments do not. Or who will protect our constitution if governments unwittingly disarm it.

The response to terror is, of course, multi-layered. It has to be that way. But on the streets of our country, violent lawbreaking is dealt with as crime. It is confronted in accordance with our constitution.

In all the debates, Britain has been absolutely right to hold fast to this course. We would do well not to insult ourselves and our processes of law in the face of these medieval delusions.

As I say, the response to terror is multi-layered. But it should not include surrender.

Sir Ken Macdonald QC, Director of Public Prosecutions, was giving the inaugural CPS lecture last night