If South Africa's first black president, Nelson Mandela, were alive, he would be celebrating his 100th birthday today.

He died in 2013 at the age of 95, and his comrades and friends have been trying to keep his legacy alive.

Sahm Venter, a researcher at the Nelson Mandela Foundation, has compiled some of the letters he wrote from prison into a book.

BBC Newsday's Lawrence Pollard has been speaking to her and Mandela's granddaughter, Zamaswazi Dlamini-Mandela, about the letters.

Dlamini-Mandela became emotional while reading a letter Mandela wrote to his children after the arrest of his then wife Winnie Madikizela-Mandela.