At this point Robertson's arguments become quite technical and legal (Mullahs has the feel of a written submission to a court, with frequent cross-reference to witness statements and other evidence, and a tidy chronology at the end). 

Violence is outlawed in international law, and to use military force without one of three recognised justifications is to commit the crime of aggression. Robertson assumes that deadlock at the UN will prohibit a Security Council resolution authorising force, and that going nuclear will not cause a humanitarian catastrophe of such magnitude that the international community must act. 

This leaves the third justification: the Caroline criteria governing a state's right to pre-emptive self-defence, where the necessity for force must be instant, overwhelming and leaving no choice of means and no moment of deliberation. Israel, he concludes, has no right to attack Iran today. Airstrikes are impractical, would only set back Iran's programme, and cause the emission of highly toxic radiological material. Israel would be acting in anticipation of a threat, before it crystallises. In any event, Iran does not pose a genuine threat. Despite President Ahmadinejad's anti-Semitic and belligerent rhetoric, Robertson concludes: "The leaders of Iran are about as rational as serial killers, and it is their criminality, rather than their rationality, that matters." 

Here he is on dubious ground. Robertson has no real suggestion on how to stop Iran. He alludes to a US-led coalition of the willing which could act, presumably with force, but immediately warns any such attack attracts a reciprocal duty on the US and its allies to treat their own nuclear weapons as unlawful and proceed to multilateral disarmament. The mullahs are not quaking at the alternative: the remote possibility of following Charles Taylor to trial at The Hague and life in a British prison (Robertson would oppose them following Saddam to the noose) once the bomb has been built.

Robertson partly built his reputation at the Bar by voraciously chasing heinous abusers of human rights. He documented this sterling work in Crimes against Humanity (1999) before lamentably chucking Benedict XVI into the same basket as Pinochet and Milosevic in The Case of the Pope (2010). Therein lies his problem. A lawyer sees proliferation through "legal architectures", NGOs and human rights. But without a consistent and reliable global enforcement authority that does not doubt the rectitude of its actions, the bomb will remain an untameable creature of the wild lands of international realpolitik.