What is clear from yesterday's long and complex judgments is that this decision - by six opinions to one - confirms the historic achievement of the first House of Lords in ruling that the armour of sovereign immunity, which has hitherto protected tyrants and torturers, has an Achilles' heel. It was located, in Pinochet's case, in the allegation that he instigated widespread and systematic torture, "a crime against humanity" which Britain, Spain and Chile had bound themselves by Convention to punish wherever it occurred. It was a crime of such unforgivable moral blackness that all the respect and dignity owed to Chile as an independent sovereign state could not be permitted to shield its former head from the consequences of his actions.
That said, the Law Lords went on to consider a special extradition point that had not been taken at the previous hearing, although it would undoubtedly have been raised in the course of the extradition proceedings (by taking it at this stage, the judges have in fact saved further delay).
Most of them found that the "double criminality" rule limited extradition crimes to those taking place after 1988. No doubt Jack Straw will be pressed with the argument that "only" three cases of torture are alleged in this later period, but he should carefully read page 59 of Lord Hope's key speech. This explains that the true significance of these particular acts was to show that even in the last years of his dictatorship "he was a party to the use of torture as a systematic attack on all those who opposed or might oppose his government". On this basis, Pinochet's mind was as guilty in 1988 as it had been in 1973 - more so, in fact, because by that later stage he had no armed opposition.
There will be disappointment among torture victims that Pinochet cannot, as a result of an obscure extradition rule, be put on trial for the murders and tortures he ordered during, and for years after, his overthrow of democracy in 1973. This is regrettable, but has one great merit: it pulls the rug entirely from under Pinochet's supporters. They have, in the last few months, created a cottage propaganda industry claiming that the General had to kill Chileans in order to save them from Cuba-style communism - that they were better dead (or destroyed by torture) than red.
This argument may be a perversion of history, but on any view it cannot apply to torture and murder in 1988, 15 years after Salvador Allende's death. There may be only three charges left in the Spanish prosecution, but they allege such a degree of indefensible wickedness - a dictator's determination to abuse his unthreatened power - that the case for extradition is overwhelming.
What has become crystal clear in recent months is that Pinochet will never stand trial in Chile. There have been cases brought against him by relatives of those who disappeared under his orders, all consolidated before Judge Juan Guzmn of the Santiago Appeals Court, who recently explained, "I am prevented from issuing any kind of arrest warrant", because of the amnesty Pinochet bestowed on himself in 1978 and because he will always enjoy immunity as "Senator for life". Even if these immunities were in some way ended, the issue of any warrant against the General would automatically remove his case to a military court, where his acquittal would be a foregone conclusion.
The other false claim his supporters make is that Chile has reached a South Africa-style "national reconciliation". It did have a truth commission, chaired by Senator Rettig, which reported in 1992 on the extent of the killings and the torture, but which was prohibited from "naming names" and identifying those responsible. Bishop Tutu's Commission was altogether different, offering "plea bargain" immunity only to those who were prepared to confess the full truth apologetically and in public, and to give evidence for the prosecution in future criminal trials.
Pinochet has never apologised, although he has joked that the "disappearances" saved the cost of coffins. If he remains out of the country, fighting extradition and then a trial in Spain, the Chilean government may have the courage to set up a proper truth commission to unmask the pre-1988 crimes of Pinochet and his executioners.
The Pinochet case marks a signal advance in international human rights law. The breach in "sovereign immunity" has been hailed by Mary Robinson, Richard Goldstone and other leading jurists, and it must not be tarnished by allowing Pinochet to return to a hero's welcome from his followers in Chile. In fact, the ruling should be followed up by making an immediate application for Idi Amin's extradition from Saudi Arabia. His position as a former head of state would not make him immune from prosecution at the Old Bailey for the murders of British citizens during his rule in Uganda.
There will, inevitably, be disappointment that Pinochet cannot be prosecuted in Spain for the bulk of his crimes, but this should be tempered by the advances the case has made in human rights law. Britain can take some credit, too, for the fact that its courts have bent over backwards to be fair to this man, compared with the utter lack of fairness he meted out to his victims who were denied any form of legal process.
At least, if there is retribution for just one family, that of Marcos Quezada Yanez, some justice will have been done.
Geoffrey Robertson QC is author of `The Justice Game', published in paperback this month by Vintage