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Daybreak correspondent Richard Gaisford reports that President Zuma is being booed by the crowd.
Boos drowning out the cheers & applause in our part of the Stadium as Zuma takes stage. He's determined to win them over. Electric start.
South African President Jacob Zuma is to give the keynote address next.
Ceremony organisers cut in with a musical interlude to drown out the boos from the crowd.
President Raul Castro says Nelson Mandela set an "insurmountable example" to Latin America and the Caribbean which he says are "currently moving towards unity and integration for the benefits of their peoples on the basis of respect for diversity".
Nick Clegg's children have created a festive doodle for the Deputy Prime Minister's Christmas card - giving the Liberal Democrat leader a Santa hat and beard.
Mr Clegg's wife Miriam Gonzalez Durantez was given reindeer antlers and Rudolph's red nose in the image, created by the three boys using an iPad to draw over a photograph of the couple on the sofa in their west London home.
The boys Antonio, 11, Alberto, nine and Miguel, four added a speech bubble showing their parents saying "Happy Christmas" and a decorated tree to complete the festive image.
Cuban President Raul Castro is speaking at the memorial service for Nelson Mandela.
He described Mandela as the "ultimate symbol of dignity and unwavering dedication to the revolutionary struggle for freedom and justice".
The trial of Abu Qatada was adjourned until Christmas Eve, following his objection to the presence of a military judge in the three-judge tribunal.
The radical cleric said the make-up of the judicial panel violates an agreement with Britain which paved way for his extradition and was meant to guarantee him a fair trial in his homeland.
He is charged with plotting terror attacks against Israelis, Americans and other Westerners in Jordan in two foiled attempts in 1999 and 2000.
In both cases, Abu Qatada was convicted in absentia and sentenced to life in prison.
But on his return from the UK in July, those sentences were suspended and he has to be re-tried under Jordanian law.
Out of respect for Nelson Mandela and his family, just observed minute's silence at ECOFIN Council in Brussels with fellow finance ministers
Housing Minister Kris Hopkins has responded to a report which warned that one working person every five minutes is being forced into claiming Housing Benefit because of soaring rents in London, while other areas are experiencing economic growth.
Mr Hopkins said: "The housing market we inherited in 2010 had housebuilding at its lowest peacetime levels since the 1920s.
"Three years later rents are falling in real terms, we've built 360,000 homes and housebuilding is growing at its fastest rate for 10 years. None of this would have been possible without our action to cut the deficit left by the last administration, and keep interest rates low."
President Obama spoke about when he first learned about Nelson Mandela at school, and of how he was personally inspired by his struggle.
Watch the finale of his well-received speech:
Crowds starting to thin in stadium at #MandelaMemorial, not keen on speeches by various world leaders and prospect of address by Jacob Zuma.