text: The star whisked through 23 songs in 90 minutes, in a blur of pyrotechnics, lasers and multiple costume changes.
  She donned silken butterfly wings for a piano-led version of ...Baby One More Time, and dressed as a ringmaster during a Circus-themed segment.
  Spears even made a passable attempt at a London accent while chatting to the audience between songs.
  "Do you wanna get norr-tee?" she teased, doing her best Sid James impersonation before launching into Freakshow - during which she dragged a (slightly over-enthusiastic) member of the audience around the stage on a leash.
  It was all great fun but, without the elaborate set pieces of her Vegas production, Spears' shortcomings were left exposed.
  Her vocals rarely seemed to be coming from the microphone, while her dancing lacked attitude and bite.
  The choreography was over-reliant on hand gestures; and Spears showed a tendency to slip in and out of time, like a clockwork doll whose mechanism had worn out.
  Her biggest blunder came during the song Touch of My Hand, as she leant over a dancer's arm to initiate a backflip, but teetered on her heels and aborted the move.
  Frustratingly, Spears showed glimpses of her former glories - pulling off a series of impressive lifts, as well as a punchy dance breakdown during Womanizer - but the routines more often felt like they were stuck in the rehearsal room.
  Tabloids will undoubtedly criticise the star for miming (the producers insist she sings over a pre-recorded backing track) but, at this point, expecting Spears to sing live is like turning up at Nando's and ordering truffles: The only person you're disappointing is yourself.
  In the end, Spears has always played second fiddle to her songs - especially in the second half of her career, following a much-documented breakdown in 2007 that means her life is still controlled by a court-approved conservatorship - and those songs provided an unshakeable foundation to her act.
  By now, the 34-year-old has accumulated enough hits to be able to dispense with ...Baby One More Time and Oops! ...I Did It Again at the top of her show, without worrying about the consequences.
  Later highlights included an energised version of Gimme More and a pounding, gothic revamp of the early single Stronger.
  The star only played one new song -  the ethereal, beatific Make Me - which may count as a missed opportunity to reinvigorate sales of her album, Glory, which tumbled down the charts to number 94 last Friday, after just three weeks on sale.
  But it was the 2004 hit Toxic that received the most enthusiastic reception from the audience, whose singing almost drowned out the loudspeakers at London's Roundhouse.
  Among the fans joining in with the Britney karaoke were Sam Smith, Rita Ora, Nicholas Hoult and All Saints singer Melanie Blatt; while thousands more were able to watch at home, as the gig was streamed as part of the Apple Music Festival.
  Spears seemed overwhelmed by the reaction, clasping her hand to her mouth and blurting out, "You guys have been amazing," as she left the stage.
  Fans may have a long wait before she repeats the show in the UK, however, with her Las Vegas residency already booking into 2017.
  The Apple Music festival continues until the end of the week, with performances from Michael Buble and Chance The Rapper.
  Setlist:
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target: Britney Spears has staged a stripped-down version of her Las Vegas residency at her first UK show since 2011.