Prince Charles joined movie veteran Robert Redford at his Sundance London festival in Greenwich this weekend to share their ideas for a more sustainable environment.

The Prince of Wales introduced the screening of the film Harmony: A New Way of Looking at Our World on Saturday during the first non-US outing for Redford’s successful film and music festival.

The documentary, by filmmakers Stuart Sender and Julie Bergman Sender, tells the story of how Prince Charles has worked with environmental activists, government, business leaders, artists, architects and visionaries to find solutions for a more sustainable environment.

Redford told the audience their shared concern “has been manifested by action. “What Prince Charles has done to commit to that ideal is just incredible.”

The Prince said he was “enormously touched and honoured” by the remarks and for Redford inviting him and bringing Sundance to London. “I think we owe him a huge debt of gratitude for that,” he said.

The four day festival closed yesterday.

Redford, who is president and Founder of Sundance Institute, said: “These four days have seen features, documentaries and live events with insightful filmmakers and musicians, as well as passionate audiences in attendance.”