Pippa Middleton scaled the Matterhorn in Switzerland to raise money for the Michael Matthews Foundation.
The foundation was established in memory of her fiancé James Matthews' late brother Michael, who died in 1999 at the age of 22 while climbing Mount Everest.
Pippa, 32, who got engaged to James in July, was accompanied by her brother James Middleton and told the Mail on Sunday: "It was humbling to have been able to climb one of the world's most beautiful mountains and raise money for a charity created in memory of an extraordinary young man who lost his life on another peak. Although I have raised money in the past for the Michael Matthews Foundation, it has now become even more important to me and my family.
"It would have been good if James had been here to share the experience, something I know he would have loved to have done. Mountain climbing, though, has disturbing memories and understandably James kept his feet firmly on the ground, whilst giving us his complete support."
Pippa revealed she and her 29-year-old brother were "honoured" to be able to pay tribute to Michael and raise money for his foundation, which builds schools in remote areas around the world.
She said: "Although neither I nor my brother ever met Michael, we both share his spirit and passion for the mountains. We made this climb knowing he would have been there nudging us on, and we are honoured to be supporting his memory."
Pippa and James previously scaled Mont Blanc together in 2008.
Tagged in Pippa Middleton James Middleton