Turning specifically to Iran, it is undeniable that the failure to locate weapons of mass destruction in Iraq leads people to believe that either the evidence that they might be there is confected or hyped or oversold, whatever. The fact that the dossier making the case for intervention is now widely described as a “false prospectus” – and that’s a sort of given – means that there’s a higher threshold if a future British prime minister or a future American president were to say that we absolutely need to take action against Iran. People would say “well, you know you’re the team who cried wolf before” and that means that strictly in terms of politics the West’s leaders face a more difficult challenge this time round.

PB: I’m afraid that’s right. We often ask ourselves what are the most serious intelligence failures since the Cold War and there have been several. Obviously the failure to prevent 9/11 must rank pretty high but I think the misapprehension of Iraqi weapons of mass destruction has been the most damaging. As Michael said, it has eroded trust at a time when trust will be the most precious commodity a leadership can bring. Acting for preclusive purposes, acting to prevent the hypothetical, requires an immense amount of trust; perhaps more trust that any leader today has. President Clinton has often said that not intervening in Rwanda was the greatest regret of his eight years in office. Suppose he had intervened, suppose he’d stopped the genocide there, if he had tried to justify it by saying he had saved 800,000 lives no one would have believed him. It sounds preposterous, people would have said: “What? With machetes? Who are you kidding?”