The arrest late on Friday by the Metropolitan Police followed a request via Interpol from judges investigating the death of hundreds of Spaniards at the hands of the military regimes of Chile and Argentina in the 1970s and 1980s.
Britain's decision to detain the former dictator, who continued to command the army until March this year when he became a life senator, was sanctioned at the highest political level in London.
Friends of his British victims are seeking to have Pinochet stand trial in this country under the Offences against the Person Act, 1861. A case against him in Britain would take precedence over any bid from Spain to have him extradited.
Gen Pinochet was travelling on a diplomatic passport, but it would have been difficult for a British government to allow a suspect to evade Interpol. The decision to arrest him was doubtless affected by mounting protests to 10 Downing Street about his stay here from his victims in Britain, continental Europe and Chile itself.
British human rights campaigners who were active 25 years ago have been reminding the Government of the cases of British surgeon Sheila Cassidy, who was tortured in Santiago shortly after the 1973 coup, and William Beausire, a British subject who was held in a detention centre known as El Discoteca because loud music was used to muffle the cries of the tortured.
The arrest of the former dictator will help re-establish the credentials of Robin Cook as a foreign secretary devoted to an ethical foreign policy at a time when they, and the left-wing credentials of New Labour as a whole, are being questioned.
But it will dishearten the British weapons manufacturers which found the former dictator an excellent client. Under the previous Conservative government, the general was a regular visitor to Britain, arriving and departing from British Aerospace's airfields.
The British link, page 16