The song is best known as the soundtrack to the 1982 animated Raymong Briggs adaptation The Snowman.
In a new interview with Metro, Blake said that his original idea for “Walking in the Air” was scrawled on the back of an envelope.
At the time of conceiving the song, he said, he had been “too busy and I had a sort of collapse”.
The composer added: “I had to get away from it all and think things through, I went and sat on a beach in Cornwall, and I lived there for about two months.
“I wanted to write a symphony about perfect innocence, the innocence with which we’re born and which we lose.
“I was walking on the beach and this tune came into my head. And I thought, ‘That’s it!’”
Blake continued: “It just came to me, and I wrote it on the back of an envelope.”
The song later went on to become the soundtrack for Channel 4’s The Snowman, after Blake had a chance encounter with film producer John Coates.
Blake said when he saw the hand-drawn images of the little boy and the snowman, he knew “that’s where that tune belongs”.
The Snowman was an immediate success after it aired in Christmas 1982. It was nominated for the Academy Award for Best Animated Short Film and won a Bafta TV Award.
The story is told through pictures, action and music, and is wordless, with the exception of the central song “Walking in the Air”. The orchestral score was performed in the film by the Sinfonia of London and the song was performed by Peter Auty, a St Paul’s Cathedral choirboy.
“Walking in the Air” was later famously covered by Welsh singer Aled Jones.