A wall of white bricks, mortar lines drawn in pale blue, stretches edge to edge with the cool indifference of graph paper. There is nothing to land on, no faces, no band, no horizon. That emptiness is the point. For the original sleeve of The Wall, that was the entire image: a barrier, blank and unbroken, daring you to wonder what it was keeping out or in.

The red lettering you see scrawled across the center came later, and it carries the only heat on the whole cover. PINK FLOYD sits high, jagged and impatient, the strokes thinning and splitting like dry paint dragged too fast. Below, THE WALL is larger, heavier, the W collapsing into the bricks beneath it. The letters drip and trail at their feet, more like graffiti or a warning than a tidy logo. On issued copies this lettering turned up either as a sticker on the wrapping or printed onto the sleeve, sometimes in black, sometimes in this alarming red.

The hand behind those marks belonged to Gerald Scarfe, a political illustrator with a long track record of skewering the powerful. When Pink Floyd asked him aboard, he was befuddled by the invitation. His relationship with the band had grown out of the Wish You Were Here tour, where he and Roger Waters got along sharing an ironic, sardonic streak. That rapport is what put a cartoonist in charge of one of rock's most recognizable sleeves.

Scarfe's arrival was no accident of taste alone. Waters had fallen out with Storm Thorgerson of the design group Hipgnosis, the team that had shaped nearly every Pink Floyd cover. The Wall became the first album sleeve since their 1967 debut, The Piper at the Gates of Dawn, not made by that group. A feud, in other words, is partly why the wall is so bare.

Scarfe described making the cover itself as quick, a doddle, designed on Waters' kitchen table during last-minute visits to the South of France. He flew down to meet the band as the album bore down on its release date, racing to draw the story's cast: the wives, the mother, the teacher, and other half-human, half-cartoon figures that filled the inner sleeve and the record labels, where the wall appears in various stages of construction. The blank front you see is only the surface. Behind it, his grotesques were already massing.

Those drawings refused to stay on paper. Scarfe's illustrations were turned into towering inflatable puppets for the album's live show, and what he called a doddle on the cover became three years of labour-intensive staging and film. The simplicity out front and the sprawling spectacle behind it are two faces of the same project: a rock opera built around isolation, released on 30 November 1979 through Harvest/EMI and Columbia/CBS Records.

The music met a divided room at first. Many critics found it overblown and pretentious, too grand for its own good. Audiences disagreed in volume: around 30 million copies sold worldwide, and Rolling Stone has placed it among the best albums ever in every decade since 2000. The wall that looked like nothing turned out to be one of the most stared-at images in rock.

Spend a moment with it and the design logic clicks. A real album cover usually wants to seduce you. This one builds a barrier between you and the record, then lets a cartoonist's red hand vandalize it just enough to let you in. The bricks are neat, the lettering is not, and that tension, order versus the scrawl breaking through it, is the whole story before a single note plays.