Prince Harry urged the world to help keep the promise his mother made to landmine victims weeks before she died.
Diana, Princess of Wales's last overseas tour was to Bosnia in August 1997 when she met victims of the weapons.
Harry quoted his mother as he gave the keynote address at a Kensington Palace reception on International Mine Awareness Day, and recalled a vow she made to two teenage boys who had suffered life-changing injuries.
He said: "As I mentioned earlier, in August 1997, my mother travelled to Bosnia with Ken Rutherford.
"When she was there she met two young boys, one Muslim, one Serbian, who had both lost legs to landmines. She shared their stories with the world, and helped campaigners, many of whom are in this room, to change history.
"Those two young boys, Malic and Zarko, are now grown men and are with us today. Twenty years on, they both still struggle with their physical and emotional injuries and with the high costs of replacing their prosthetics.
"When my mother said goodbye to Zarko that August, just weeks before her untimely death, she told him he would not be forgotten.
"Please help me keep her word to Zarko and Malic, and other people like them throughout the world, who still need us to finish the job and rid the planet of landmines."
He added that if Diana was alive today she would not be willing to accept any credit for the fact the Ottawa treaty was signed by 122 states in the same year that she visited Angola and Bosnia.
After his speech, Harry spoke to Malic Bradoric, 33, who now has a four-year-old son. He said: "Perhaps we can meet again when the world is landmine-free. I will be 40 by then."
Zarko Beric, 34, spoke fondly of the day he met Diana, recalling: "I was so surprised when I saw her. I could not believe my eyes - it was a princess, wearing blue jeans. I remember her words when she was leaving. She told us, 'You are not going to be forgotten'.
"What she said gave me a lot of strength whenever I have had hard times. When she got killed I could not believe it. I felt like a part of me had disappeared. I had a sinking feeling."
Harry is continuing to champion Diana's cause, just months ahead of the 20th anniversary of her death.
The Prince, who became patron of the HALO Trust's 25th Anniversary Appeal, has followed in his mother's footsteps by visiting minefields in Angola and Mozambique.
Just months before she died in a car crash in 1997, Diana, wearing a protective visor and vest, walked through an Angolan mine field being cleared by the HALO Trust.
She spoke out against the sale and use of landmines and famously called for an international ban on the devices during her trip, which led to the then junior defence minister Earl Howe branding her "ill-informed" and a "loose cannon that Her Majesty's government did not need".
Recalling her words in a speech she gave two months before her death, Harry told those gathered: "In June 1997 at a seminar organised by Mines Advisory Group and the Landmine Survivors Network, my mother said in a speech - 'Even if the world decided tomorrow to ban these weapons, this terrible legacy of mines already in the earth would continue to plague the poor nations of the Globe. The evil that men do, lives after them...'"
The global drive supported by Harry to rid the world of landmines by 2025 is to receive £100 million of government funding.
International Development Secretary Priti Patel announced that the UK was tripling its backing for demining as she addressed the reception.
The HALO Trust and another anti-landmine charity, the Mines Advisory Group, called on governments across the globe to deliver on their promise to eradicate the lethal explosives within eight years.
They estimate that £100 million will be needed globally every year to make the world mine-free by 2025.