Prime Minister David C ameron and US President Barack Obama pose for a selfie alongside Danish Prime Minister Helle Thorning-Schmidt (left) at the memorial service for Nelson Mandela - prompting an outpouring of criticism. The world leaders, attending the historic service to honour former South African leader Mandela in Soweto today, smiled as they leaned in for the snap... while Obama's wife Michelle looked non-plussed as she declined to join in. The U.S. president was also seen sharing jokes with the Danish PM, although his wife seemed less than impressed (inset centre). Earlier, President Obama shook hands with Cuban President Raul Castor, an unprecedented gesture of friendship between the Cold War enemies. He also paid an emotional tribute to Nelson Mandela, calling him a 'giant of history' as he spoke in a stadium where around a third of the seats were mysteriously left empty (bottom right). Mandela's widow Graca Machel sat three seats apart from his ex...