Appearing on behalf of Halo Trust, a British organization that removes landmines and other debris left over from war, the 32-year-old royal shared an impassioned keynote speech that he began by referencing Diana's trip to visit victims of the global catastrophe, months before her death in 1997.
"Twenty years ago, in the last months of her life, my mother campaigned to draw attention to the horrific and indiscriminate impact of landmines," Harry shared, detailing the late princess' travels to communities in the Congo, Bosnia, and other areas vastly affected by landmines.
"She met with those who had suffered life-changing injuries as a result of anti-personnel mines, she listened to their stories, and helped share them with the world," he continued.
Later in his speech, Harry shared a story of Diana's meeting with young survivors of landmine explosions, whose stories she would later tell to the world.
"When she was there she met two young boys, one Muslim, one Serbian, who had both lost legs to landmines," he explained. "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," Harry told the room. "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."
To close, Harry offered up a final request on behalf of Diana: "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."
The speech wasn't the only public appearance that Harry made this week. On Wednesday, he attended a somber service of hope for the victims of the recent London terror attacks alongside Prince William and Kate Middleton.
Though Harry and his older brother, William, may have certainly inherited their mother's passion for charity, it wasn't always easy for the brothers to speak on her death.
Last December, Harry officially opened up about losing his mother and admitted to burying his emotion for several years.
"I now view life differently from what it used to be," he confessed in the documentary Prince Harry in Africa. "I used to bury my head in the sand, and let everything around you tear you to pieces. I was fighting the system, going, 'I don't want to be this person.'"
"My mother died when I was very, very young and I don't want to be in the position," added Harry. "Now I’m so energized, fired up, to be lucky enough to be in a position to make a difference."