Robbie Williams might as well have swaggered onstage polishing his big metal testicles. Orff's Carmina Burana, reworked around the singer's name, thundered round the NEC on this first night of a 21-date, five-city tour as a prelude to Robbie's emergence; meanwhile "public announcements" counted down the minutes to lift-off. The anticipation, like the hype, is palpable. That he starts his set with Let Me Entertain You - as much a plea as an offer - and then confesses "I'm shitting myself" demonstrates the contradiction at Williams's heart.

The nation's favourite cheeky chappie is a neurotic superstar who needs his audience as much as they worship him. He may dress up his showmanship with raised eyebrows and camp glances - as if it's all a bit of a larf - but, for Williams, pleasing the crowd is a serious business. It is almost a compulsion.

Not that he needs to worry: the audience was more than willing to bless him with their affection. As well as what was once Williams's core audience - teenage girls in capri pants with carnal thoughts beyond their years - the crowd was swollen with adolescent boys flushed with testosterone and in search of a role model, burly blokes in their 20s in much the same predicament, and more burly blokes in their 40s who probably also had tickets to see Tom Jones.

Middle-aged women ("Let me entertain you, Robbie," one shouted lustily after Karma Killer) completed the smorgasbord of the Great British public, all hollering along to Strong, No Regrets and the latest single - Kids, his duet with Kylie - with unfettered enthusiasm. This audience certainly lends weight to the notion that if there's a cultural icon that unifies Britain right now, it isn't the Royal Family or Coronation Street, it's Williams. Once an underdog, he's now the mutt's nuts.

Still he frets, though, protesting too much with his ironic, devil-may-care attitude. Williams's tongue remains so firmly in his cheek for so long that, if the wind changes, he may stay that way. And that would be a shame, since the bloke from Stoke is at his best when he is most genuine - a heartfelt rendition of She's the One is one of the night's highlights.

All his cowboy-punk-Elvis posturing dangerously obscures Williams's formidable vocal talents, not to mention the excellent songwriting for which he and writing partner Guy Chambers are responsible. They are undoubtedly two of the most important British music writers since Lennon and McCartney - and, live, Williams and his band (including Chambers on keyboards) do their songs every justice, adding rather than obscuring nuance and subtlety. Indeed, this was the first time I considered No Regrets could be about Williams's relationship with his estranged father, not simply a tormented love song.

Yet Williams's first encore once more betrayed the karaoke king as he burst into My Way before segueing into his own singalong classics, Millennium and Angels, which the crowd crooned nearly by themselves. Williams was well chuffed. There's another song that Williams might consider for next time, instead of Carmina Burana. It's called Manic Superstar.

• Robbie Williams is at the NEC, Birmingham (0121-780 4133), from tomorrow until Saturday, then tours.