How do you describe the view to someone who can’t see? I couldn’t even do justice to a canal towpath

How many shades of green are there? Whatever the answer may be, I soon ran out of words to describe them. I was walking north along the Grand Union canal, trying and failing to adequately describe what I could see, to a friend who couldn’t. This was Dave Heeley, ultra-runner, who in 2008 became the first blind person to run seven marathons on seven continents in seven days. Today we were walking rather than running – which, with me guiding him, was just as well.

I had guided a blind adventurer once before when I took part in the television series Pilgrimage. One of my fellow pilgrims was the remarkable Amar Latif. We were high up on the side of a deep, lush valley in eastern Serbia. I was focused on the trickiness of the path itself, but Amar kept asking me to describe the vista. I looked down that valley at the mountains in the distance and simply didn’t know how or where to start. I had a........

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