40 Years After Dark Side: 'Not one of my favourites,' says the man behind the prism

The stark but simple image of a prism on a black background is a far cry from the bombast of a giant pig flying over Battersea power station or flaming businessmen. Yet the cover of Pink Floyd's classic 1973 album The Dark Side of the Moon is probably one of the most instantly recognisable ever made.

Yet despite bringing its creator, Storm Thorgerson, universal acclaim and the record becoming one of the biggest selling of all time, it doesn't rank as among his favourite designs. "It's not a favourite, pictorially – what we did with it later is more fun," the designer said from his home in north-west London. "To be associated with such an amazing album is great. But from an artistic point of view, I'm more interested in photographs."

Thorgerson, now in his sixties, has been friends with several of the original members of Pink Floyd since their Cambridgeshire school days. After forming the art design group Hipgnosis with another Cambridge native, Aubrey Powell, he went on to produce some of the band's most striking album covers, including the floating pig above Battersea Power station for the album Animals. He has also designed covers for other bands including Led Zeppelin and, more recently, the Scottish rockers Biffy Clyro.

As Pink Floyd began recording The Dark Side of the Moon at Abbey Road studios, they demanded Thorgerson do something different for them compared with his previous covers. Rick Wright, the group's keyboard player, ended up insulting the designer by saying: "Why don't we not have one of your tacky pictures, Storm?"

"I said, 'Well, Rick, tacky pictures is what I do' and I got very huffy about it," he said. "Rick said, 'Let's have something graphic, cool and deliberate.' I was so angry." In the end, the idea came from a shop window.

"I was passing a bookshop and saw an image of a prism. It wasn't the same [as the one on the cover], but I remembered the prism from school and the refracted spectrum and thought maybe that would work. It was about light, which was featured in their show; the triangle is a symbol of ambition which was in the lyrics and the prism is also a common property – except I made one big change. I made the background black and it makes all the difference."

After showing the band several rough designs, which he had worked on with the artist George Hardie, they immediately settled on the prism.

The record brought the band previously unknown wealth, but for Thorgerson, he hints, less so. "It changed their lives drastically, but not mine so much."