Chapter seven of The Wind in the Willows is called The Piper at the Gates of Dawn. As every good hippy knows, that’s also the name of the debut album by Pink Floyd, a prime cut of 1967 psychedelia so adventurously spaced out that it makes even the cross-dressing weirdness and trippy harmonies of the band’s first singles, Arnold Layne and See Emily Play, seem conventional by comparison.

In his short eulogy to the Floyd’s wayward genius Syd Barrett, playwright Alan Bissett makes the connection between Kenneth Grahame’s children’s classic and the acid-damaged songwriter who would soon be forced to leave the band because of mental ill health. It’s partly that, like Little Portly, the missing otter in The Wind in the Willows, Barrett was “always straying off and getting lost, and turning up again”. But it’s also that, underscoring the band’s early work, there’s a very English streak of whimsy in the tradition of Grahame’s literary fantasy.

The Barrett we find in One Thinks of It All As a Dream is a fey, home counties romantic, his head split between the quietness of the countryside and the mind-altering noise of rock’n’roll. Played by Euan Cuthbertson with eye-liner, mop of curly hair and dangly shirt sleeves, he is all soft-spoken charm and dreamy unpredictability. He’ll strike a pose of pop-star grandeur, arms outstretched as if on a crucifix, then deflate the pomposity with a look of surprise and a coy, self-mocking grin. As mental illness takes hold, it’s the self-awareness that goes.

Facebook Twitter Pinterest All soft-spoken charm and dreamy unpredictability … Euan Cuthbertson as Barrett

The set by Jonathan Scott places us at that precise point in the 60s when the Mondrian-inspired oblongs, squares and triangles of designer Yves Saint Laurent were colliding with an explosion of hallucinogenic colour, playfully replicated by lighting designers Ross Kirkland and Chris Reilly. As order gives way to chaos, Barrett’s bandmates go from fellow stoners to concerned onlookers. They’re up for the prog-rock party, playing as dawn breaks as part of the 14 Hour Technicolor Dream fundraising gig, but less happy about sharing a stage with an increasingly erratic lead singer.

Sacha Kyle’s production captures the way a group of polite, young, middle-class men negotiate a line between hedonism and hard work. As bassist Roger Waters, Andrew John Tait is the most ready to put business before pleasure, but Ewan Petrie as keyboard player Richard Wright and David James Kirkwood as drummer Nick Mason (also doubling as maverick psychiatrist RD Laing) need little persuasion to leave their chief songwriter behind.

Bissett’s script has its clunky moments of exposition (“In a week, we’ll have left grammar school”) as it skips fluidly around the band’s early career. But in a show supported by the Scottish mental health arts and film festival, it does a good job in going backwards to consider the trauma of Barrett losing his father as a teenager and forwards to see how his legacy of mental ill health would haunt the band in work such as Shine on You Crazy Diamond, Brain Damage and The Wall.

• At Òran Mór, Glasgow, until 22 October. Box office: 08444 771000. Then touring until 5 November.