Mystical warriors and prog rock monsters, Yes would be the first to admit they are better at playing their instruments than looking good for photos.

They would surely also concede that much of their success comes down to their brand identity (not that the free-thinking cosmic adventurers would have used the term to describe their sleeve designs and bubble logo).

The visionary mind behind the cover art and fantasy look was Sussex-based artist Roger Dean.

He admits The Beatles (with their misspelt name) and The Who (with their arrow) had certain visual codes, but believes Yes were the first British artists to pioneer an all-encompassing look.

“All the early Elvis Presley albums would have him on the front. He was his brand identity,” Dean explains.

“With a band like Yes that didn’t work – you had to have some graphic expression of who they were, and that had to have the feel that it was the band.

“So we tried to get a visual metaphor, not just for the music, but for the band themselves.”

The managing director of Atlantic Records had been impressed with Dean’s work with Gun and invited him to meet Yes.

Dean had seen them on tour and thought the way they looked and did their merchandising was “amazingly random”.

“I can remember in America you would get three or four guys turn up in vans and they would hustle their way to the front of the queue to sell stuff and Yes’s manager would do some deal and whoever bid the most, sold the T-shirts.

“This was stuff they had ran up, so there was no consistency in look or quality, it was awful.

“Similarly, I was seeing from the back of the theatre that Yes were not an active band; the sound was good but the experience was not visual.

“I thought they had to have a stronger visual identity, so I designed the logo and, in 1973, we designed them a stage set and that took the idea way beyond an album cover.”

Dean, whose skills extend to architecture (his grand plans for Brighton Marina never materialised but his work for the upstairs interior of Ronnie Scott’s Jazz Club were a success), interior design (a “retreat pod” chair was featured in A Clockwork Orange) and publisher (he’s overseen millions of sales of books of commercial art), designed all the classic Yes covers.

Relayer – an album with the 22-minute epic The Gates Of Delirium featuring a cosmic battle inspired by Leo Tolstoy’s War And Peace – and Tales From Topographic Oceans, a double vinyl based on frontman Jon Anderson's interpretation of the Shastric scriptures – remain Dean’s favourite sleeves.

Relayer appears to be a grey watercolour and ink painting with three horsemen riding on a pathway under chalk-coloured arches. Similarly, the path running through Tales From Topographic Oceans looks like a lunar landscape under a night sky.

“They had a simplicity I liked,” says Dean of the sleeves. “Both are very complicated ideas but at first glance they looked like very simple paintings.”

Dean calls himself a landscape artist, inspired by architecture. When he worked for Yes, Rick Wakeman and Uriah Heep, he had just finished an academic thesis on what kind of spaces make humans feel good. This inspired his style – and still does.

“I had looked very carefully into the choreography and psychology of pathways, and I know that sounds like nonsense but the most exhausting mile you could walk would be, say, an airport runway. But put a row of trees either side of it and it’s a different experience.

“So I was looking at what made pathways interesting – how they had to twist and turn, how you have to keep opening up new and surprising vistas, how you had to go over and under things, how pathways worked in urban settings and natural settings, and bridges as well because people have a terrific emotional rapport with bridges.

“I was doing all this and this led to photographing pathways in mountains and in wild places and it was something I brought into the art.”

Although he says art and music have a perfect relationship – “when they come together they make a new thing which is enhanced by both”

– they are separate.

“You can listen to the music and not suffer for not seeing an album sleeve.”

He never works from a record – “I don’t paint music” – but does find talking to musicians a source of inspiration.

“The joy of working with musicians is they don’t try to art direct. They focus on what they have to do. We talk about ideas, sources of inspiration and they let me get on what I want to do. I just paint what I want to paint.”

A selection of Dean’s work will be exhibited beside work by his daughter Frejya.

The exhibition runs at Trading Boundaries, Sheffield Park, from September 27 to October 13, Monday to Saturday, 10am to 6pm, call 01825 790200