The 20th anniversary of Diana's death will be commemorated on Thursday and the royal brothers, with Kate, earlier honoured her memory by visiting a nearby memorial garden in the grounds of the palace created for the Princess.
During the visit, Kate, William and Harry were given a tour by the head gardener, along with a gardener who knew the Princess from her frequent visits there.
The garden became a place for thousands of mourners to leave flowers and memorabilia after Diana died in a vehicle crash in Paris in 1997.
They then met a few representatives from some of the main charities Diana worked with in the final years of her life, including Great Ormond Street Hospital, the National Aids Trust, The Leprosy Mission, Royal Marsden Hospital, English National Ballet and Centrepoint.
However the White Garden is set to be one of the most iconic memorials yet, with tributes from the public already being left for Diana at the Kensington Palace gates ahead of the anniversary tomorrow. We hope the statue will help all those who visit Kensington Palace to reflect on her life and her legacy'.
William, 35, and Harry, 32, stood looking at photos and floral tributes left for their mother at the Golden Gates of the palace.
But the scene is nothing like the sea of flowers laid in the week between her death and her funeral: an outpouring of national grief that commentators are still grappling with.
A public that had lapped up every twist and turn in the life of their fairytale princess was crying for their lost icon, killed in the chase for the next day's pictures. But, apparently, she didn't let that misery stop her from confronting Prince Charles and Camilla about their affair.
Diana's close friend Sir Elton John performed "Candle in the Wind", written in her honour.
Angela Silva, 66, has briefly left her London restaurant to leave a bunch of coloured roses, "not as big as the bouquet I left before, 20 years ago", she says.
Second in line to the throne William said: "She was this ray of light in a fairly grey world".
"And I wouldn't let it break me".
"I really did expect more people to be here, maybe more will come in the afternoon", she adds.