Ernesto "Che" Guevara may be an icon of revolution to millions, but for Alberto Granado he was a friend. He tells the story of their extraordinary friendship for a BBC Two documentary.
In 1952 two young men from Argentina set off to explore South America on a motorbike.
Alberto remains an "admirer" of his old friend
Their journey forged a life-long bond and changed them forever.
Alberto, whose trip was made into the recent film The Motorcycle Diaries, says he still turns to Che for advice - nearly 40 years after his death.
"He never forgot me and I never forgot him either," the biochemist in Cuba told the BBC.
"His personality is so strong it is impossible to forget him - especially me."
The future travelling companions met in 1942, when Alberto was 20 and Che was 14.
Back then Alberto could already foresee that Che would become an important person.
"What I appreciated most was his honesty - and his ability to transform negative things into positive things," he said.
They were natural companions, but Che was not an easy friend.
"He was not compromising. It wasn't easy unless you shared his vision and believed in it," Alberto said.
The restless young men turned a long-time dream into a reality when they set off on their motorbike "La Poderosa" in 1952.
They crossed from Argentina into Chile, where they quickly ran out of money and were forced to become "motorised scroungers", as Che put it later.
The pair had to blag and charm their way across Latin America - relying on the goodwill and hospitality of strangers.
La Poderosa finally broke down in Los Angeles, Chile, so the friends continued their trip by boat, horse and lorry.
For Alberto, it was a terrible moment.
"It was like saying goodbye to someone you love," he said.
'Doctor of the people'
The journey also opened their eyes to inequality.
"The trip made us aware of poverty and wealth," Alberto said.
Fidel Castro and Che Guevara brought communism to Cuba
"The most important thing was to realise that we had a common sensibility for the things that were wrong and unjust."
Their week at the leper colony of Sao Paulo in the Amazon proved pivotal.
The pair shared everything with the sick people, he said.
"I got the impression that Che was saying goodbye to institutional medicine and becoming a doctor of the people," he recalls of his friend's wave on their departure.
In Caracas they parted, after nine months together. Alberto stayed on in the Venezuelan capital to work on research into leprosy, while Che went to Buenos Aires to graduate as a doctor.
Later, Che moved to Mexico, where he met the future Cuban leader Fidel Castro. In 1956 they invaded Cuba with a revolutionary army.
After the success of the 1959 revolution, Che invited Alberto to Cuba.
For Alberto, it was easy to make a home in the country he "had always dreamed of".
Cuba is a place "where people aim to improve themselves from a scientific or artistic point of view", he said, "instead of always thinking about consuming".
After the Cuban revolution, the friends went their own ways.
"Che chose the road to liberation," Alberto said.
Che remains a symbol of defiance
He rebuts the speculation about whether Che's departure from Cuba was prompted by arguments with President Castro or the Russians.
"He just wanted to cause a revolution in Latin America."
More than 37 years after Che Guevara's execution in Bolivia, his face is still emblazoned on thousands of t-shirts and posters, and the legend is kept alive in books and films.
"He was always worthy of what he said, thought and did - that's why they use Che's image," Alberto said.
And he remains an "admirer" of his old friend.
"Our journey, the Cuban revolution and Che have made me what I am now," he said.
"When I have doubts, I ask myself what Ernesto would say."