In 1970, when Dezo Hoffman produced this stylised portrait of Scott Walker, the 27-year-old singer was, as he would later admit, entering a long period of creative decline. Having been a reluctant pop star in the mid-1960s as lead singer of the Walker Brothers, a trio dubbed “the American Beatles”, he had embarked on a singular solo career as a balladeer whose style encompassed American show tunes and the more expressive songs of his hero, the Belgian chansonnier Jacques Brel.

In retrospect, Walker’s early solo albums are among the greatest, and most unlikely, second acts of 1960s pop stardom. Scott (1967), Scott 2 (1968) and Scott 3 (1969) sold surprisingly well despite being willfully out of step with the psychedelic experimentalism of the time. In 1969, he was even given his own BBC series, Scott, on which he sang Broadway standards and Brel ballads as well as his own material. That same year, he released Scott 4, an album written, he later said, “on drink” and entirely made up of original songs. Now recognised as one of his greatest recordings, it sold poorly. The world was not ready for the existentialist musings of a pop singer whose touchstones were the films of Kurosawa and Bergman and the novels of Kafka and Camus.

For the next five years, capitulating to record company pressure, he produced a series of increasingly lacklustre albums made up mainly of cover versions. In 1970, around the time this picture was taken, he had just released the first of them, ‘Til the Band Comes In, which comprised one side of original songs, the other of covers – an all-too-obvious exercise in creative compromise. “I should have stopped,” he later said, “I should have said, ‘OK, forget it’ and walked away.”

The Walker you see here is still allowing himself to be portrayed as a pop star: stylish, cool, languorously sexy. But there is a faraway look in his eyes. In his head, he is already elsewhere. It would take him some time though to trust his instincts.

Following a brief, but surprisingly creative, Walker Brothers reunion in the mid-70s, Walker went silent. Nothing was heard of him for five years. Then came 1984’s Climate of Hunter, an album that announced one of the great third acts in popular music, a creative rebirth that eschewed any notion of commercial compromise. On subsequent albums Tilt (1995), The Drift (2006) and Bish Bosch (2012), he travelled as far away from pop as is possible to go, into texture, dissonance, silence. “Essentially, I’m really trying to find a way to talk about the things that cannot be spoken of,” he told me in 2008.

In person, he was as deeply serious about his art as I expected him to be, and yet engaging and friendly despite his obvious diffidence. I put it to him that his music might be drifting towards the final, everlasting silence. “Perhaps,” he replied, nodding, “perhaps.” Now he is gone and his music echoes defiantly against that silence even as it anticipates it. It is difficult to think of another musical journey as singular or, in the end, as uncompromising.