Harry, repesenting the Queen, joined senior politicians including Mr Cameron and Labour leader Ed Miliband and religious leaders at the service in Westminster Abbey celebrating the life and work of Nelson Mandela, who died on December 5 aged 95 years old.
The service heard South African singing and drumming and an address by Kgalema Motlanthe, South African deputy president, and Peter Hain MP, the anti-apartheid campaigner.
Others present included former British Prime Minister Sir John Major and members of the Cabinet including Health Secretary Jeremy Hunt and Speaker of the House of Commons John Bercow.
Church leaders attending included the Archbishop of Canterbury the Most Rev Justin Welby and the leader of Catholics in England and Wales Cardinal Vincent Nichols.
In an address to the congregation, the Most Rev Tutu, the former Archbishop of Cape Town thanked "splendid" anti-apartheid campaigners for their efforts in changing the "moral climate" over apartheid.
"What would have happened had Mandela died in prison as was the intention and hope of the upholders of apartheid," he said. "I suppose most would have regarded him as no better than a terrorist."
Singling out the anti-apartheid movement for praise, he thanked those who had picketed South Africa House, the South African High Commission in London during the apartheid years and those who had supported a "long haired" Mr Hain in his battle to boycott South African sport in the 1970s.