First Night: Christina Aguilera, Koko, London

Only a fool would bet against Christina Aguilera's successful return. If last month's cover shoot for American GQ and lucrative deals with Sony Ericsson/Orange mobile phones were the prep work for her latest campaign, her still-sublime, four-octave voice, and sassy, hook-laden new single "Ain't No Other Man" should take care of the rest.

We're told the 25-year-old's new double album is partly "a throwback to Twenties, Thirties and Forties-style jazz and blues", but it's not quite adieu to "Xtina", the leather chaps-wearing minx who built up such a head of steam on 2002's Stripped. While Back To Basics pays musical homage to the likes of Etta James and Aguilera's current platinum blonde look is pure 40s Hollywood glamour á la Marilyn Monroe, tracks such as "Still Dirrty" are hardly coy. You suspect that, were Aguilera to let her skirt balloon-up over an air-vent, she'd probably have nothing on underneath.

In person she's a charismatic, if unshakeably diminutive character, her gold high heels taking her to about 5ft 3in. Most of this is legs though - something you can't help but notice given Aguilera's tight - fitting black shorts. Joined by an ace cast that includes a horn-section and a troupe of sassy dancers, she opens with the single, and then dedicates "Understand", the powerful, waltz-time ballad, "to a certain man in my life who I love very much". This is music executive Jordan Bratman, her husband since November 2005.

Things get a whole lot sexier on "Candy Man", another new track somewhat reminiscent of Madonna's "Hanky-Panky", but with tight, 1940s-style vocal harmonies. Aguilera has now donned a white and navy-blue sailor's hat and set it at a jaunty angle, and she signals the song's end with an animated, almost vaudevillian wink.

In some ways, it is more like watching a video-shoot than a gig, but hey, vive la difference. There is a lot to be said for glamour, meticulous burlesque-style choreography and a set that doesn't look like it was designed on the back of a fag packet. Like the premature veteran she is (our host had nailed every riff and note of Mariah Carey's "Vision Of Love" by the age of 10, remember) Aguilera owns her stage, her every bump and grind cognisant of eyes that scrutinise her as closely as any camera. When she lets loose on her 2001 hit "Lady Marmalade", moreover, you are reminded she, rather than her collaborators Lil' Kim, Mya and Pink, was the vocal dynamo of the record.

"Oh Mother", Aguilera tells us, is about her own mother. "She got us out of a domestic violence situation at home," adds the singer, whose parents divorced when she was seven. "I've only sung this song a couple of times, and whenever I do, I have to stop myself from crying." With "Beautiful" and "Slow Down Baby" concluding matters, Aguilera's set is finished in 30 minutes, but less is undoubtedly more. She went for the easy emotional score at times, but with its vocal athleticism and super-slick delivery, this was a pop diva master class.