Charles chatted privately with the Titanic actor after they were given guided tours by designer Stella of her sustainable items in a gallery at COP26. Leonardo’s appearance caused a buzz around the UN climate conference in Glasgow as rumours surfaced on Tuesday he was attending, before he was finally spotted.

       The actor is a climate change campaigner, working on a number of documentaries about the environment, and was appointed a United Nations representative on climate change in 2014.

       The trio spoke together for around 10 minutes at Glasgow’s Kelvingrove Art Gallery, where garments included handbags made from lab-grown mushroom leather.

       Stella said Charles found her exhibition “enlightening and inspiring”. She added: “I want to highlight my industry and call it out. I’m trying to provide sustainable solutions.”