Speaking before the Cardiff memorial, at which she read Yeats' poem He Wishes For The Cloths Of Heaven, the Duchess said: "I think the whole world was taken by the tragedy of Ben and Catherine, who were taken away at such a young age".
Sarah has also agreed to become a patron of the Mullany fund, a charity set up in memory of the late couple to help finance prospective medical students and physiotherapists. Ben, 31, was a trainee physiotherapist and his new wife, also 31, was a GP. The Duchess has already donated £10,000 from the Sarah Ferguson Foundation.
"They were so in love and so happy…" she said. "It is just an extraordinary story."