Mutya Keisha Siobhán take the stage in this tiny studio to rehearse the new single ‘Flatline’ to an audience of two. It’s a weather-beaten slice of pop soul about a fading love affair, a lot more knowing and less polished than the shimmering singles of their youth. They step up to their microphones, they move in sync, they harmonise, they swap wide-eyed sideways looks of delight. Their backing band fires up the riff to Gary Numan’s ‘Are Friends Electric?’ and they steam into ‘Freak Like Me’, Siobhán now singing the Heidi Range lead part as she did at the well-reviewed Scala gig earlier this month. I sit and watch from the balcony, fascinated, at a whole new chapter in a soap opera that’s rolled on for 15 years — more than half their lives. The standard cliché is about a lost childhood, but I can’t help thinking that this is the reverse: three people who had their childhoods extended by never being allowed to be independent. If they lost anything, it was their adulthood.