Former US president Barack Obama was set to deliver a speech to a crowd of 15,000 people in South Africa on Tuesday as the centrepiece of celebrations marking 100 years since Nelson Mandela’s birth.

Obama has made relatively few public appearances since leaving the White House in 2017, but he has often credited Mandela for being one of the great inspirations in his life.

He will deliver the Nelson Mandela Annual Lecture at a cricket stadium in Johannesburg at 1245 GMT in an address set to urge young people to fight to defend democracy, human rights and peace.