All around the O2, the posters and flashing billboards reminded us that Britney Spears’s first UK shows in five years were something other than a mere arena show. If you wanted to be reductive about it, you could argue that The Circus Starring Britney Spears merely alluded to the singer’s current album (also entitled The Circus). However, for the most Googled person on the planet, the imagery was excitingly apposite on all sorts of other levels. Lest we forget, a circus is a travelling show where strange and freakish spectacles unfold before you on a stage, possibly featuring heavily sedated creatures who don’t seem entirely sure of their surroundings. For anyone who remembers Spears’s infamous MTV Video Music Award “comeback” less than two years ago, there’s no need to dwell on the resonances here.

But at this biggest of big tops, it was a more alert Spears who descended from the rigging on to the biggest of the three circular stages in a saucy ringmaster’s get-up. Performing The Circus she negotiated a human tide of cavorting dancers dressed in burlesque bondage gear and freakish masks. Was she really singing? A debate that has rumbled on in newsprint and internet forums since the tour began three months ago wasn’t easily settled by watching her lips.

Certainly, even without any big screens to help to decide the matter, you registered the lack of any apparent physical exertion as she got to grips with her stinging anti-paparazzi address Piece Of Me. By the same token, there were times when it felt churlish to mind: the lavish Bollywood shakedown of Me Against The Music; the sheer randomness of a version of Toxic which involved freighting modified metal bedsteads at speed across the stage. And who wouldn’t have chosen to lip-sync on Ooh Ooh Baby — whose set piece saw the 27-year-old mother of two climb in a box and have her entire torso seemingly shunted to the left of the rest of her body. In what constituted something of a high point, the song then segued into Hot As Ice, which saw Spears seemingly teleported 30 yards without the tassled platinum dress she had been wearing seconds before.

It was a set heavily reliant on the last two albums — a surprise, in a sense, given the events in her life that they have soundtracked. By the same token, a chief signifier of Spears’s iconic status is that the more dramatic her life becomes, the better material she seems to inspire from songwriters. Propelled by almost subsonic hip-hop beats, Get Naked (I Got A Plan) truly came into its own.

But postmodern as you tried to be about the whole singing/not singing debate, it was hard not to feel an hitherto-absent frisson of emotional engagement on the occasions when she obviously was. Everytime was a case in point. Whatever other problems she has encountered in her tempestuous life, vertigo certainly isn’t one of them.

Perched on the hook of a precariously suspended umbrella, she received one of the biggest cheers of the evening for a performance of Everytime that came, if not from the heart, then from the diaphragm.

Such moments of old-fashioned entertainment notwithstanding, it was the sheer timeless ubiquity of Baby One More Time (and possibly the fact that she was performing it in leather lingerie) that elicited the biggest roar. That she returned dressed as a kinky policewoman for Womanizer was no disaster. As she set about admonishing the errant cad in the song, she imperiously waved her truncheon at any passing dancers who happened to come too near to it.

If the overheard chatter of the departing throng was anything to go by, 90 minutes of lavish costume changes, camp choreography and cabaret club magic just about mitigated lingering doubts concerning the veracity of her singing. If she did mime, perhaps it didn’t matter. After all, don’t mime artists also belong in a circus?

Tour continues: O2 June 4 until June 13; Manchester MEN Arena, June 17 (www.britneyspears.com/tour )

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