Prince William spoke movingly about his mother, the late Princess Diana, in a rare, emotional and public speech at the 21st anniversary dinner of the charity, Child Bereavement UK, tonight.

“My mother was determined to help those in need and she would have been immensely proud – as I am – of all that Child Bereavement UK has achieved these last 21 years,” the second-in-line to the British throne said, paying tribute to his mother, who helped launch the charity in 1994.

“Fifteen years later, I was honored to be invited to become Patron of Child Bereavement UK to continue my mother’s commitment to a charity which is very dear to me.”

The charity, which is run by Julia Samuel, one of the late Princess Diana’s closest friends and the godmother to 2-year-old Prince George, assists children of military families, those of suicide victims, terminally-ill parents whose children need support coping with their inevitable death and other children devastated by the loss of a parent.

“What my mother recognized back then — and what I understand now — is that grief is the most painful experience that any child or parent can endure,” Prince William said, alluding to the pain he felt when his own mother tragically died in 1997.

William rarely speaks publicly about his mother, but tonight, he honored her work and compassion. Prince William told guests that “when many people slink away at the sight of a friend’s bereavement,” the charity’s staff embraces strangers at the darkest moment in their life.

The charity’s impact is even more important to Prince William now, as a young father.

“As a father to two young children myself, I now appreciate it all the more,” he said.

Both Prince William and Prince Harry are patrons of some of their mother’s most meaningful charities and are determined to keep her legacy alive.

The Charity Child Bereavement UK charity event was part of a busy day for His Royal Highness. The Duke of Cambridge spent the afternoon at the Cambridge University college, where he studied agriculture, and met with professors.

Prince William told professor Christopher Dobson that at six months Princess Charlotte was very “ladylike,” and Prince George very “lively,” and called both of his children “delightful.”

The Duke and Duchess of Cambridge have had an active fall, filled with public engagements, and William has juggled his royal responsibilities with his job as an air ambulance pilot. Next week, the Duke and Duchess will participate in the State Visit of the President of China supporting the Queen. While the Palace does not announce guests in advance, it is expected that the Duchess of Cambridge will attend her first State Banquet and London is abuzz about which tiara and jewels she may wear for the occasion