South Africans were praised for the "dignified" way in which they have commemorated the death of Nelson Mandela as the memorial service for the anti-apartheid hero got under way.
Thousands of ordinary South Africans sang God Bless Africa - Nkosi Sikelel'i Afrika - as they joined leaders at the FNB stadium in Soweto amid driving rain.
ANC deputy president Cyril Ramaphosa welcomed leaders from countries around the world.
"We wish to applaud the people of South Africa for the dignified manner in which they have honoured and remembered the memory of Nelson Mandela since he passed away. We applaud you and thank you for it," he said at the start of the service.
Those attending included Prime Minister David Cameron and his three surviving predecessors, Sir John Major, Tony Blair and Gordon Brown.
Also seen arriving at the service were supermodel Naomi Campbell, rock star Bono, former South African president FW De Klerk, ex-US secretary of state Hillary Clinton and former French president Nicholas Sarkozy.
Mr Mandela, who died last Thursday aged 95, made his last public appearance at the stadium at the closing ceremony of the 2010 football World Cup.
Members of the audience got to their feet and waved South African flags in spite of the downpour.
The service heard from Andrew Mlangeni, a former prisoner on Robben Island with Mr Mandela, who spoke of the "outpouring of love" following his death.
"Madiba is looking down on us. There is no doubt he is smiling and he watches his beloved country, men and women, unite to celebrate his life and legacy," he said.
The thousands of people gathered in the stadium will hear speeches from statesmen including US President Barack Obama, UN Secretary-General Ban Ki-moon and South African President Jacob Zuma, who will give the keynote address.
Asked what lessons leaders could learn from Mr Mandela, Mr Cameron told the BBC Radio 4 Today programme: "I think the classic lesson is that there is never a wrong time to do the right thing and that his generosity, his forgiveness, I think, was so important in bringing people together and there are so many parts of the world, in fact all parts of the world, where we need that sort of attitude.
"But there will be a lot of leaders upstairs who will be watching this and I hope that that's the lesson we take away."
The Prime Minister and Mr Brown were among MPs who paid tribute to Mr Mandela in a special Commons session yesterday following the Nobel peace prize-winner's death.
Mr Cameron said Mr Mandela was a "towering figure in our lifetime" and added: "When looking back over history, it can be easy to see victories over prejudice and hatred as somehow inevitable.
"As the years lengthen and events recede, it can seem as though the natural tide of progress continually bears humanity ever upwards, away from brutality and darkness and towards something better. But it is not so.
"Progress is not just handed down as a gift, it is won through struggle - the struggle of men and women who believe things can be better, who refuse to accept the world as it is but dream of what it can be. Nelson Mandela was the embodiment of that struggle.
"He did not see himself as the helpless victim of history - he wrote it."
Mr Brown added his tribute to "the man that taught us no injustice can last forever".
"Nelson Mandela, the greatest man of his generation, yes, but across generations, one of the most courageous people you could ever hope to meet," he said.
After the memorial service, Mr Mandela's body will lie in state at South Africa's seat of government, the Union Buildings in Pretoria, until he is laid to rest in a state funeral at his home town of Qunu in the Eastern Cape on Sunday.
The Prince of Wales will be among a smaller number of dignitaries travelling to the remote rural location for that service.