Most pet cats will become timid or defensive when outdoors, but not Millie – after being adopted by her mountain-climbing owner Craig Armstrong, Millie has become a feline hiking and mountain-climbing legend.

Audrey Lu and Misha Mitrofanov of the United States compete in the Pairs Short Program during day 1 of the ISU Grand Prix of Figure Skating Rostelecom Cup at Megasport Arena on November 15, 2019 in Moscow, Russia. (Photo by Maxim Shemetov/Reuters)

Marc Berthod of Switzerland during the Audi FIS Alpine Ski World Cup Men's Super Combined on February 12, 2012 in Sochi, Russia. (Photo by Vianney Thibaut/Agence Zoom/Getty Images)

People dance to celebrate Midsummer Eve during sunset at the Amager Strandpark in Copenhagen, Denmark, June 23, 2021. (Photo by Hannah McKay/Reuters)

A woman reacts as anti-government protesters place a dead body on a stretcher after violence erupted in the Independence Square in Kiev, in this February 20, 2014 file photo. (Photo by Vasily Fedosenko/Reuters)

Image of the Clouds taken in August 2014 by astronauts on board the International Space Station (ISS). A year from space photographs of hurricanes, typhoons and meteorite craters show an astronauts-eye view of our planet from hundreds of miles above the earth. The illuminating images were taken by astronauts onboard the International Space Station (ISS) over the course of 2014. (Photo by NASA/SPL/Barcroft Media)

UK Love Island's star Megan Barton Hanson, 26, looked incredible as she stripped off for a very sеxy shoot to mark her return to Only Fans on March 20, 2020. The latest pictures see the stunning star pulling a range of poses while wearing just yellow thong lingerie and a pair of black boots. (Photo by Backgrid UK)

A female tourist wears a protective face mask on the street, following an outbreak of the coronavirus disease (COVID-19), in Tokyo, Japan on March 10, 2020. (Photo by Hannibal Hanschke/Reuters)