Daniel Johnson: I thought we’d start with Philip’s striking thesis in Terror and Consent that everything we thought we knew about terrorism and how to deal with it is obsolete and we must start again. It’s a very radical view. Why do you think that?

Philip Bobbitt: Terrorism is the name of an epiphenomenon, a symptom of the state. Different constitutional cultures and orders produce different forms of terrorism. Perhaps the most vulnerability-making quality of our constitutional culture is our refusal to realise that it and the kind of terrorism it produces are undergoing a fundamental change. So we bring the habits of mind of a century of success against terrorism and they are just as inappropriate as those of the French knights  who walked onward to Agincourt.

DJ: Michael, what do you think of that? Can the British claim to have learnt something with their long struggle with the IRA?