When General Pinochet was arrested in London in the quiet time before midnight on 16 October 1998, relatively few British people knew who he was. He had not been ruler of Chile for approaching a decade; the world since the end of the Cold War was confusingly full of ex-dictators; and Chile seemed a fairly minor and obscure place, a very long way away. Still fewer people in Britain, most likely, were aware that he was in the country. The fact had been noted here and there in the newspapers, but it was a busy time of year, and Pinochet had visited Britain just the previous autumn, and intermittently throughout the 1990s, each time attracting sparse comment. This time, it had actually taken the British press several weeks to register the general’s presence at all. On 25 September, at the Dorchester Hotel in central London, he had been photographed for an interview for The New Yorker, the American magazine, standing bulkily to attention in a dark pinstripe suit as five bodyguards loitered off-camera around the hired suite and on its veranda. Yet it was not until 10 October that a Foreign Office confirmation of Pinochet’s ‘private visit’ to Britain appeared as three paragraphs in the Guardian. And when the Pinochet issue of The New Yorker came out, three days later, the parts of the interview that mentioned Britain were still regarded as a surprise and a scoop and were quoted as such in British newspapers.

As for why an eighty-two-year-old South American, of French descent and seemingly alien politics, who spoke almost no English, should regard Britain as his second home – this remained most mysterious of all in the autumn of 1998. Before his arrest, and in more detail immediately afterwards, a certain amount appeared about the general’s British itinerary prior to the arrival of two plainclothes policemen at his bedside in the London Clinic. As well as having surgery there for a spinal hernia, he had been to Madame Tussaud’s. He had visited the National Army Museum and had lunch at Fortnum & Mason. He had bought books about Napoleon at Foyle’s on Charing Cross Road. He had had a talk with the head salesman at Burberry.

But all this trail constituted, in a sense, was the schedule of a fairly typical wealthy tourist: some old-fashioned and eccentric shops, a museum or two, and some discreet medical treatment. Pinochet’s habitual ports of call in London were places that were so specifically styled and polished for foreign consumption that they revealed only a little about the nature and depth of his attachment to Britain. The London Clinic, for example, could have been chosen for its proximity to the Chilean embassy, a couple of streets away past the actually rather un-British Marylebone mansion blocks, with their prim shutters and dusty little balconies. And apart from the clinic’s brass desk lamps and milky net curtains, it was really just another immaculate and anonymous international private hospital. Pinochet’s first choice had actually been in Paris, but the French refused him a visa.

What he wore while he was still at liberty in London also sent out ambiguous signals. On the one hand, in the scraps of television footage of the general benignly buying newspapers and admiring passing red buses, there was his jacket. It was conservatively tailored, long in the back and generous in its vents and lapels, and of the precise shade of country brown, achieved with small checks of beige and black and chocolate, found only in English gentlemen’s outfitters. There was also his shirt (pale and striped), and his tie (bright red). With his white moustache and pinkish face, his odd broken blood vessel and cannonball head, Pinochet could have passed for a retired British colonel of a certain sort. Or at least from the waist upwards: in his shiny black shoes and spotless chinos he was perhaps a little too dapper, and in his walk there was a grandness, an almost ceremonial deliberation in each slow, heavy step. It suggested parade grounds, but not the part-time British sort.

Once he was under guard, Pinochet’s presence in Britain felt all the more like a borrowing from a strange novel. There was his brief convalescence at the clinic, as armed policemen tried not to alarm its many floors of recovering millionaires, and the first besieging stockades of anti-Pinochet protesters arranged themselves raucously around the entrances. On the same crammed pavements, there were the first counter-demonstrations by Pinochet’s supporters, who looked bafflingly like ladies from Chelsea. Next, there were his undignified few weeks at Grovelands, a private nursing home in north London. It looked grand behind railings in the middle of parkland, but the suburb around it (Southgate) was modest enough, with its semis and out-of-date shops, to seem like a punishment. And the Grovelands staff, it was rumoured, did not find the general the easiest or most convincing patient; in the end, the self-styled ‘saviour of Chile’ had to be told he was better and asked to leave.

And then there was Wentworth. The feared former dictator confined to an executive home, on a vainglorious private estate designed for golfing tycoons. From the winter of 1998 until the early spring of 2000, among the pines and electric gates of primest Surrey, with the clatter of protesters’ pots and pans carrying through the trees every Saturday, and jets leaving Heathrow airport droning tauntingly low overhead … Pinochet read his books on Napoleon and surfed the Internet. Only once did he attend a brief court hearing, at a high-security prison in south London. As he was driven there and back, his bodyguards held up jackets against the car windows to protect him from photographers. A beige blanket was draped over his head, as if he were a rapist or a paedophile.

The rest of the time, at Bow Street Magistrates’ Court and the House of Lords and the High Court, on all the airless stage sets of this melodramatic and unprecedented episode of international litigation, the general was a ghost. As the case veered erratically about, his name was invoked so often it became more of a moral shorthand. His actual person became less familiar than the papier mâché version.

Until, abruptly, he was gone. On the damp grey morning of 2 March 2000, before anyone could get more than a glimpse of the back of a blue people carrier and an escort of police cars, Pinochet had been slipped up one of Wentworth’s private roads and out of an unattended side entrance towards the motorway. By eleven o’clock, the blank little motorcade was well on its way, between wet fields and Lincolnshire hamlets, to a remote RAF base and a Chilean jet keeping its engines warm behind the perimeter fencing. On the radio, a perplexed presenter was saying: ‘Two years ago I wouldn’t have dreamed of asking this, but do you, as chairwoman of the National Association of Women’s Institutes, have a line on General Pinochet?’ By lunchtime, the ex-dictator had taken off into the mist. Another presenter was summarising wearily, as if at the end of a long royal procession: ‘So, there we are, the departure of Augusto Pinochet from this country.’ Rain dotted the lenses of the few cameras present. The lunchtime news programmes turned away without offering a conclusion.

The mystery of General Pinochet has endured pretty intact since. The idea that his 503 days in British custody were prompted and steered by anything other than foreign grievances and chance – a lucky initiative from a Spanish magistrate investigating old abuses against his fellow citizens, a country that happened to be receptive, an area of international law where there happened to be no consensus – has not been entertained much. The Pinochet case, it has been generally agreed, was about state torture and murder in a far-off land; the incompatible interests of those who suffered or approved; and how the law, Spanish or British or Chilean or international, might help these competing groups to live with each other in a narrow strip of land on the other side of the Andes. The moral enormity and legal complexity of all this, and the further unexpected developments in the Pinochet case since he returned to Chile, have been more than enough to take in. But every now and again, there have also been hints of an additional dimension.

In October 1999, the Prime Minister, Tony Blair, while insisting that the question of Pinochet’s extradition to Spain would be decided by his government on purely legal grounds, also told the Labour Party conference that he found him ‘unspeakable’. Peter Mandelson, a politician not noted for his outbursts, publicly declared that if Pinochet evaded extradition it would be ‘gut-wrenching’. And Jack Straw, who as Home Secretary was personally in charge of the case, turned out to have another Chilean connection: in the late 1960s, as a left-wing student, he had spent several enthusiastic weeks in the country, meeting the sort of liberal Chileans that Pinochet would spend the next decade persecuting. The daughter of the most famous of these, Salvador Allende, Marxist president of Chile from 1970 until the general’s coup killed him, was invited – a quarter of a century later – to the 1998 Labour Party conference. Isabel Allende had dinner there with the Prime Minister. ‘He told me he thought my father was a hero,’ she said afterwards.

Perhaps all...