Stars of the screen, stage and sporting arena paid tribute on Friday to Nelson Mandela, whose visit to London has been overshadowed by events in Zimbabwe where disputed elections have just ended.
Hollywood actor Will Smith hosted the birthday celebration in front of Mandela, who turns 90 next month, and nearly 50,000 fans in London's Hyde Park.
Smith was followed on stage by Formula One racer Lewis Hamilton and pop acts Leona Lewis, Annie Lennox, Razorlight and some of Africa's biggest singers, while Simple Minds and Amy Winehouse were among those still expected to perform.
The event was organised to support Mandela's HIV/AIDS charity "46664", named after his prison number, and comes 20 years after the city hosted another concert for the statesman when he was still behind bars for his stand against apartheid.
"Twenty years ago, London hosted a historic concert which called for our freedom," a frail-looking Mandela told the cheering crowd after they had sung him Happy Birthday.
"Your voices carried across the water and inspired us in our prison cells far away.
"As we celebrate, let us remind ourselves that our work is far from complete. Where there is poverty and sickness, including AIDS, where human beings are being oppressed, there is more work to be done.
"Our work is for freedom for all ... We say tonight, after nearly 90 years of life, it is time for new hands to lift the burdens. It is in your hands now, I thank you."
The tribute to Mandela coincides with disputed elections in Zimbabwe, and during his trip to Britain Mandela was urged to speak out against President Robert Mugabe who pushed ahead with the vote despite international outcry.
Opposition leader Morgan Tsvangirai boycotted the poll because of a wave of deadly attacks on his supporters.
FOUR WORDS RESONATE
During his visit, Mandela uttered just four words of criticism of Zimbabwe in a speech at a dinner -- "tragic failure of leadership" -- and they were enough to make headline news.
Mandela, South Africa's first black president, officially retired from politics nine years ago, but he is still a moral authority admired the world over.
People in the crowd appeared to be at the gig more to honour Mandela than to hear the music.
"I'm here because of the man," said Clive Jones, a 31-year-old theatre technician. "I feel he's done so much for the world, especially with what was happening in South Africa. He is also humble and kind."
Emmanuel Jal, a Sudanese hip-hop artist based in London who is singing on Friday, said Mandela was "unique" among African leaders. "He did not love power so much, and left it and gave it to someone else," he told Reuters.
Jerry Dammers, who helped organise the 1988 concert and whose song "Free Nelson Mandela" became an anthem for the anti-apartheid movement in Britain in the 1980s, will also take the stage.
One of the highlights is expected to be soul singer Winehouse, who is due to appear despite being diagnosed with a "touch of" lung condition emphysema earlier this month.