"There is comfort in remembering. In acknowledging that, while taken horribly soon, they lived. They changed our lives. They were loved, and they are loved. It is why memorials such as the Glade of Light are so important. Why Catherine and I so wanted to be amongst you today.
"Catherine and I know that the atrocity's impact will last a lifetime and beyond, and that the healing process is still ongoing. We want to assure all of you who are struggling that you are very much in our thoughts."
The Duke and Duchess of Cambridge then took a walk around the memorial garden where the Duchess placed a bouquet of flowers.
The royal couple later shared a tribute on Twitter saying, "there is comfort in remembering.
"In acknowledging that, while taken horribly soon, they lived. They changed out lives. They were loved, and they are loved.
"It is why memorials such as the Glade of Light are so important. Why Catherine and I so wanted to be here today."
The unveiling comes almost a year after the royal brothers unveiled a bronze statue of Diana in Sunken Garden in July last year.