It’s hard to believe Stephen Sondheim is turning 90. Anyone with a modicum of interest in musical theatre over the last 65 years will know him as the brilliant star that burst over Broadway with lyrics to West Side Story, then as the composer-lyricist who redefined the art form in works like the mould-breaking Follies, the wistful A Little Night Music and the grisly Sweeney Todd.

Stephen Sondheim, 1977. Photo © Everett Collection Inc/Alamy Stock Photo

As a writer, Sondheim epitomises craft. His lyrics are sharp, smart and immaculately formed, a reassuring trove of eloquence, wit and insight. A restless self-critic, even now he can tut at an internal rhyme like “it’s alarming how charming I feel” in a song like I Feel Pretty. It’s too clever by half for a Puerto Rican immigrant with limited English, he says. In a recent New York Times interview ahead of the new Broadway production of West Side Story he was asked for a line that truly satisfied him. “I just met a girl named Maria,” he answered, adding “that’s the kind of lyric that belongs in this show, for these characters. That’s poetry.”

But, to paraphrase...