With the turmoil of three months ‘in previews’ and gossipy leakage over cast changes and backstage bickering which might warrant a musical in itself, Dusty has become London’s off-West-End equivalent of Spiderman. But not even industrial-strength bungees could save this turkey from an early Christmas.

The jukebox musical has become such an easy and familiar formula that it’s often underestimated. To succeed, you either have to deliver such blood-pumpingly authentic versions of a hugely popular back catalogue that people are dancing in the aisles, or tell a brutally truthful warts-and-all story about the star in question.

Do both, and you have Beautiful. Do neither, and you have Dusty.

Although possibly the most expensive yet at Charing Cross Theatre, the staging is strange but the book is quite simply terrible. A weak Wikipedian summary of the events in the first half of Dusty’s life with none of the passion and drama is delivered as an interview with her best friend Nancy played by Francesca Jackson in a Leslie Ash wig and a flatness of expression that could earn her a desk in a Job Centre.

It’s almost as though she’s sullen at not being cast as Dusty – which she might have been as her vocals are closer to the admittedly unmatchable Springfield’s than lead Alison Arnopp who competes unsuccessfully with ill-synchronised black-and-white BBC TV footage and the strangest holograms of Dusty largely with her back to the audience.

Apart from some farting brass notes and the feedback-distorted sound, the band aren’t bad, and they work well as characters in the story. Léo Elso even looks a bit like Tom Springfield, and Witney White shows real class singing as Martha Reeves even though the sexuality she shared with Dusty is unexplored.

It’s what’s left out of the book that’s so shocking, given that simply Googling ‘Dusty Springfield Lesbian’ would throw up a couple of dozen interesting episodes and at least two serious partners not mentioned here. Dusty needed pills and vodka to embolden her advances to other women at a time such things could have broken her career, but they also lost her some great chances – Elton John originally planned to duet ‘Don’t Go Breaking My Heart’ with her, she was offered ‘Killing Me Softly’ before Roberta Flack, and Carly Simon replaced her singing ‘Nobody Does It Better’ when she couldn’t pull herself together to record the Bond movie track.

She was violent and self-harming, she spent time in a ward at Bellevue mental hospital in New York, she had a screaming match in the street which was calmed down by Billie Jean King, she demanded her rubbish be cut up into equal-sized pieces for the bins and in her later life watched Bonanza in German all day on television and ate only cauliflower and ice cream. Did she really have an affair in Mustique with Princess Margaret?

Crazy. But wonderful theatre. If you could script it, you’d have a show to rival End of the Rainbow, Peter Quilter’s smartly-plotted Judy Garland musical.  It could be worse: Kristin Chenoweth announced in 2005 she would play Dusty in a biopic. Fortunately it never saw the light of day.

And who was the guy at the back who broke into hollow laughter at the leaden line “I’ve made my peace with disappointment a long time ago”?  Probably the producer.