This year marks the 50th anniversary of the Off-Broadway premiere of Hair, originally billed as the American tribal love-rock musical, at New York's Public Theatre.
In the years in-between it has had many more Broadway and West End incarnations. In London it originally transferred to the Shaftesbury in 1968 with a cast that included a young Elaine Paige, Marsha Hunt, Floella Benjamin, Oliver Tobias, Richard O'Brien and Tim Curry. There have also been a short-lived revival at the Old Vic in 1993 and an import to the Gielgud in 2010 for a revival that had begun at the Public Theatre's outdoor Delacorte Theatre in the summer of 2008 before transferring to Broadway.
Now it returns, rather fabulously and inspiringly, to its alternative roots, not being revived in a plush West End venue but a grungy venue carved out beneath a railway viaduct under Waterloo station called The Vaults.
I've never been much of a fan of this space in the past - but somehow it suits and fits this show like a hippy braid. You really feel you can let your hair down here, as well as your defences, partly because the actors and the audience are such in an intimate proximity to each other, but also because of the show's own sense of spirited spontaneity and informality.
Director Jonathan O'Boyle, who first directed this spirited production at Manchester's fast-rising Hope Mill Theatre last November, and his choreographer William Whelton (who is also the co-founder of Hope Mill), have maintained and enhanced its gorgeous, in-the-moment vibe and warmth.
The plot, which revolves around the compulsory drafting to the army of Claude, one of the hippy youths known as the Tribe, is pretty threadbare; but as a peg for one of the most alluring and memorable pop rock scores in musical theatre history, to hang itself off, it does its job.
And a youthful, uninhibitedly talented cast more than do theirs; it is led by Robert Metson as Claude, Andy Coxon as Berger and Laura Johnson as Sheila who bring an unfettered innocence and charm to these glorious songs.
The Vaults have also been radically transformed into an immersive space - the auditorium is festooned with multicoloured ribbons - and by the end all barriers between stage and audience have fallen away as both dance together for a grand finale. It is exhilarating and thrilling in equal measure.