Just 30 years ago, on Monday, October 9th, 1967, in the Bolivian hill town of Vallegrande I watched while two doctors cut into the body of Che Guevara with their scalpels. One fitted a small rubber tube to pour preserving liquid into a corpse barely four hours cold.

Hovering nervously behind the doctors was a plump, balding man, known to the Bolivian officers as Eddie Gonzalez, though it was later revealed that his name was Gustavo Villoldo.

He was a Cuban exile, working for the CIA, who acted as a liaison between the front-line Bolivian troops, based at Vallegrande, and the large training camp 200 km away, that was controlled and organised by 17 American Green Berets brought in from the Panama Canal Zone.

This was the first time in three years that Che Guevara had appeared to public gaze. He had "disappeared" from Cuba in April 1964, and although there had been many reports of his movements, no one knew for certain where he was or where he had been. Now, his dead body lay before me on a makeshift table.

Apart from the CIA man, I was the only person at this strange scene who had seen Che Guevara alive. I had to verify that this was indeed him. I had met Guevara in Havana in 1963, six months before his "disappearance". With good contacts in the Latin American left, I had received reliable information at the beginning of 1967 that Guevara was in Bolivia.

When the Bolivian guerrilla movement came to life in March that year, I was sure Guevara was there. This seemed to be confirmed when Regis Debray, a well-known French intellectual and confidant of Fidel Castro, was detained in Bolivia in April after visiting the guerrilla camp.

From neighbouring Chile, I had followed details of the guerrilla campaign in Bolivia week by week.

In August I travelled up by train from the Pacific coast into the Bolivian Andes, and journeyed through the most sensitive areas of the country, the tin mines, the Yungas, the Beni, and the guerrilla zone in the tropical east of the country between Camiri and Santa Cruz de la Sierra.

Che Guevara had issued a stirring call to the left of the Third World "to create two, three, many Vietnams", and I wanted to investigate whether Bolivia was capable of becoming "another Vietnam". This was the period when the US was sending tens of thousands of its own troops to fight in Vietnam, and gradually becoming bogged down. The Americans were finding it difficult to extricate themselves from this dangerous and open-ended commitment. Could the same thing happen in Bolivia?

I went to interview Douglas Henderson, the US ambassador in La Paz. "No," he said. "American combat troops will only come to Bolivia over my dead body." Henderson managed to keep his word. The enhanced American presence in Bolivia was confined to an emergency military training mission of 17 Green Berets. A couple of experienced CIA agents, both Cuban exiles, were also deployed.

Then, in September in Vallegrande, I interviewed the senior Bolivian commander in the field, Col Joaquin Zenteno Anaya. He told me, with maps, exactly where he believed Guevara's guerrilla band to be. Guevara was reported to be asthmatic and sick, and it was clear from the maps that his small force was encircled. The Bolivian officer was quietly confident and, with the imminent arrival at the front of fresh troops from the American training camp, it seemed the end was close. Bolivia's chances of becoming a "second Vietnam" seemed close to zero.

On October 7th, I had visited the Green Beret training camp at a sugar mill outside Santa Cruz. I interviewed its commander, Col "Pappy" Shelton, a veteran of the Korean war. He had sent his trained men into the field the previous week, and he too was expecting results. The following evening I was tipped off by one of Shelton's Green Beret officers that Guevara had been captured. "He has been wounded," I was told, "and may not last the night."

With two colleagues, I hired a four-wheel-drive jeep and we drove through the night to Vallegrande, in the eastern foothills of the Andes. We arrived at 9 a.m. Although we knew that Guevara was being held at the village of La Higuera, some 40 km away, no amount of bullying or bribery could get us past the military barrier on the edge of the town. We had to content ourselves with waiting at the small airstrip, while a single helicopter made repeated trips to the guerrilla zone, bringing back the corpses of dead soldiers.

Late in the morning a small Dakota flew in from La Paz, bringing the Bolivian commander-in-chief, Gen Alfredo Ovando, and other members of the High Command. Soon after 1 p.m., at an impromptu press conference on the steep cobbled streets of the town, Col Zenteno announced Guevara was dead.

Four hours later, a las cinto de la tarde, the helicopter returned from La Higuera with a single body tied to one of the landing rails. It landed on the far side of the airstrip, far from the waiting crowd, and was loaded on to a closed Chevrolet van which drove off at speed. Miraculously, I had encountered a priest from New Zealand with an old car, and we piled into it and drove fast across the airstrip and up the muddy track into the town. The van turned into the entrance of the Senor de Malta hospital.

Soldiers guarded the iron gates and tried to close them against us. But the intrepid priest got through. The van screeched to a halt, the back doors opened, and the CIA agent, Gonzalez/Villoldo, climbed out. He shouted to no one in particular, and in English, "Let's get the hell out of here!"

The corpse on a stretcher was carried out and placed on the flat basins of the hospital laundry, a small covered hut in a field, entirely open on one side. To begin with, there were only half a dozen of us, but quickly a crowd gathered from the town.

They had recently grown accustomed to the display of dead soldiers and dead guerrillas. Here was just another guerrilla fighter, bearing marks of worry and anguish on his face, his clothes and body caked in blood, his feet clad in some strange home-made moccasin. I had no doubt that this was Guevara, though he was smaller and thinner than I remembered, and his beard was blacker.

After pausing for a while, as one of my colleagues, Brian Moser, took photographs in the fading light, we headed back to Santa Cruz. There were no cable or telex facilities in Vallegrande in those days, and we had to get back to some important centre in order to send out our exclusive reports.

Eventually I had to fly on to La Paz, to make absolutely certain that my telex to my newspaper, the Guardian, would arrive safely and make the front page. "US intelligence agent in at the death of Che Guevara" read the headline.

My colleague's photographs were not the romantic ones that later went round the world, depicting Guevara with the wide-eyed appeal of a mediaeval Christ. His pictures were much darker in mood, more prosaic, and more horrific. Only recently, thanks to a spate of new biographies, have I been able to piece together why this was so.

Although the Cuban agent and I could verify that this dead guerrilla was indeed the Guevara we had once met, the Bolivian military authorities were worried, and remained so all week, that the world outside would refuse to believe the news of his death. That night they ordered the doctors to clean up the body, and to make it presentable for the press.

All that day, hearing the preliminary reports of Guevara's capture, the press descended on the Bolivian capital, La Paz. On October 10th a planeload was flown to Vallegrande and taken to view the body at the laundry hut.

There journalists took the famous photographs of the angelic Guevara that girdled the globe. One was oddly reminiscent of the famous painting by Mantegna of the recumbent (and foreshortened) Christ.

The Bolivian officers had convinced the world that Guevara was dead. Yet at the same time, by cleaning up the body and making it so beautiful, they had made an error. The haunting photographs helped to launch a legend, turning the image of Guevara into a revolutionary icon that has lasted from that day to this.

The military had made a second error. In ordering Guevara's body cleaned up, they had not imagined that his jacket would be removed and that his torso would be left bare. By doing just that, the doctors had inadvertently allowed the bullet-hole on Guevara's breast to be shown to the world's cameras. Gradually the news leaked out that Guevara had been executed after capture.

On the Monday we had been led to suppose that he had died of his wounds. Now, for the first time, it was immediately clear to the eagle-eyed that he had been executed in cold blood. At the very moment on Monday morning when I had been vainly seeking permission to travel on from Vallegrande to La Higuera, Guevara had been shot dead.

The Bolivian authorities, once so keen to display the body, were now anxious to whisk it away. Yet doubts were still being expressed. Was this really the body of Guevara? Fingerprint experts and Guevara's younger brother were reported to be on their way to Bolivia from Buenos Aires.

The doctors were ordered to make a plaster cast of Guevara's face, and on Tuesday night they attempted to do so. But they were inexperienced in this specialised task. The face of the corpse was burnt off by the hot wax, leaving it unrecognisable. The corpse could neither be viewed nor kept above ground any longer.

The order came from the military to cut off Guevara's hands. At least his fingerprints could be compared with those held by the Argentine police. Finally, in a ceremony organised on Wednesday morning by Villoldo, who was to remain in Vallegrande until the end of the week, Guevara's cadaver was taken from the hospital and buried under the airstrip. It remained there until it was dug up earlier this year. Now, 30 years later, it rests finally in Guevara's adopted homeland of Cuba.

For many years my report about the involvement of the CIA in the Bolivian campaign led people to believe that the CIA had played a crucial role in the defeat of Guevara.

Initially the Americans were rather silent. For political reasons, they had to maintain the fiction that the Bolivian armed forces had played the major role. More recently, however, other institutions - the US army and the State Department - have begun to play up their own role.

A new book, The Fall of Che Guevara, to be published early next year by Oxford University Press, and written by Henry Ryan, a retired American diplomat, argues convincingly that the CIA's activities in Bolivia were minor.

Ryan, who has made extensive researches into American archives, believes that the information the CIA fed back to Washington was often tendentious and inaccurate.

He thinks that Ambassador Henderson and Col Shelton made a greater contribution to the defeat of Guevara than the two Cuban exiles.

He's probably right.