"Little did he know the price he would pay," he told ABCNews.com. "A free South Africa became synonymous with his name, and that was what the public expected of him."
But Mandela has as many earthly passions as political ones: In his prime, he was a notorious lady's man, a boxer and a lover of ballroom dancing. His lust for life mesmerized celebrities, as well as little people.
"What you get is what you see," said Steward, now executive director of the de Klerk Foundation. "He's not putting on an act.
"If he was just walking down the street or on the way to go into the Union Building, he would speak to the gardener and express genuine interest in his life," he said. "This would cut across all racial divides. He had just as much concern for the flight crew of the presidential aircraft as he would for anybody else.
"It was not an affected charm. He is incredibly thoughtful and considerate in his relationships with the humblest of people around him. He is a great reconciler."
Those closest to him said Mandela's humanity sprang from a sense of duty that was cultivated by his noble African roots, as well as a life beset with hardship, loneliness and betrayal.
As a martyr for democratic South Africa, he spent 27 years in prison, cut off from his four children.
Released from prison in 1990, Mandela emerged into a world in motion: Africa was engulfed in an AIDS crisis -- his son Makgatho and two other family members later died of complications from the disease -- and his own nation was poised to embrace majority black rule.
Mandela credited imprisonment with strengthening his character and giving him focus, and reconciliation with his white captors became a theme of his life.
Just last week, Mandela held a private dinner celebration to mark the anniversary, inviting family and friends, including Christo Brand, one of his warders at the Robben Island prison, where he spent most of his years of captivity.
Born in 1918 in the Eastern Cape village of Transkei to a branch of the family known as the Left Hand House, Mandela was expected to be a traditional adviser to the chief of the 2.6 million-strong Thembu nation.
Sent to English schools where he was given the name "Nelson," Mandela had a deep admiration for the principles of the British parliamentary system.
As an activist with the ANC, Mandela led a general strike in 1950. He was later charged with treason in the longest trial in South African history.
When police shot 60 black protestors dead in the Sharpeville massacre, the ANC radicalized and Mandela formed the military wing and became its first commander in 1961.
By 1962, he was imprisoned for inciting a strike and sentenced in 1964 to life in prison.
George Bizos, his friend of more than half a century, said Mandela's "noble birth" had shaped his respect for others, even his foes.
When Bizos, who is white, first visited Mandela on Robben Island prison a month after his conviction in 1964, no fewer than eight white guards surrounded the prisoner on all sides. After enthusiastically embracing his friend, Mandela politely turned to his captors.