Robert Colquhoun and Robert MacBryde, the two Roberts of Damian Barr’s title, were working-class Scottish artists who met in 1933 as first-year students at the Glasgow School of Art. They lived and travelled together, created still lifes and portraits, enjoyed a run of successes and had a moment of celebrity in the legendary postwar Soho of Henrietta Moraes and Francis Bacon. But a combination of self-destructiveness and a refusal to play careerist games meant both died relatively young and in poverty. Their lives are full of promise for biographical fiction, but also present the usual challenges for any writer attempting to reconstruct lives lived, of necessity, in the shadows.

There is certainly material: Roger Bristow’s thorough joint biography, The Last Bohemians (2010), and the archives of the Glasgow School of Art. But there is much for Barr to invent and speculate about. The two Roberts had an active and varied erotic life. Buttons cut from the uniforms of countless soldiers and sailors formed a private record. But they were wary of leaving legible evidence of their relationship, burning sketches and letters. Barr turns the gaps in the record into an opportunity. Among his successes are his engaging reconstructions of MacBryde’s childhood and the role of the early mentors (teachers, librarians) who gave him his love of art and insisted, in the face of a sceptical family, on his talent and promise. Also compelling is Barr’s imagining of the men’s domestic arrangements in Glasgow when living as lodgers in the attic of the wealthy old socialist activist Mrs Cranston.

Barr has fun conceiving how the Roberts’ friendship and artistic collaboration might have crossed the line from their early pretence – even with each other – that they were ‘just two students on the same course saving on rent’ into a romantic and sexual partnership. The moment of transition is