Where was Nelson Mandela when Desmond Tutu predicted he would be prime minister?

When Desmond Tutu predicted that Nelson Mandela would become prime minister, Mandela was imprisoned at Robben Island. Tutu made this prediction in the context of the anti-apartheid struggle in South Africa, emphasizing Mandela's leadership and vision for the country. Mandela's eventual release in 1990 and subsequent election as president in 1994 fulfilled Tutu's foresight.