Prince William and Prince Harry will mark the 10th anniversary of their mother Diana's death this week.
Camilla, the duchess of Cornwall, is to stay away from the televised memorial service, which the princes are staging in honour of Diana, Princess of Wales.
The Duchess made the U-turn after fierce criticism for accepting the invitation offered to her by William and Harry.
She said she did not want to detract from the purpose of the day.
Her presence was always going to be controversial, with some adamant it was inappropriate for the woman who had an affair with the Prince of Wales while he was still married to the princess to be there.
Camilla said in a statement: "I'm very touched to have been invited by Prince William and Prince Harry. I accepted and wanted to support them. However, on reflection, I believe my attendance could divert attention from the purpose of the occasion which is to focus on the life and service of Diana."
PA