The former South African president will visit Althorp, where she is buried, to pay his respects to Diana and her humanitarian work, on 1 November.

The event is being organised by the Nelson Mandela Children's Fund, which helps children with Aids, and the Diana, Princess of Wales Memorial Fund.

A memorial fund spokeswoman said: "Two of the greatest humanitarian names of recent times will be uniting for a great cause."

Mr Mandela and Diana met in 1997

The fund has told supporters in a letter: "Nelson Mandela has let us know that he wants publicly to express his admiration for the humanitarian work of Diana, Princess of Wales, particularly in combating the stigma of HIV/Aids and bringing neglected issues to public attention."

Diana met Mr Mandela in South Africa in 1997.

After her death he called her one of the "best ambassadors for Great Britain", and said South Africans were "devastated by the news".

On 2 November, Mr Mandela will attend a dinner at Spencer House in London with Diana's brother, Charles Spencer.

Tickets will cost from £1,000, with all proceeds going to the Nelson Mandela Children's Fund.