As the crowd assembles at the O2, you don't have to look far for evidence that Rihanna long ago turned from an R&B star into a huge mainstream pop phenomenon.
There are parents here with young children in tow, their faith in the singer's ability to provide family entertainment undimmed by her reputation for raunch that recently led County Down farmer Alan Graham to insist she cover herself up while filming a video on his land.
Furthermore, she's succeeded in attracting the kind of people who never normally go to gigs, something you can tell by the fact that a number of them can be seen outside the venue, filming the entrance to the O2 Arena on their cameraphones, like over-enthusiastic first-time holidaymakers taking photos of the baggage carousel.
An audience like this comes for the hits and the grand spectacle. They get both, often at the same time. You get to see Rihanna perform Only Girl in the World while writhing seductively in a giant neon-lit hamster ball; playing a drum solo; belting out Shut Up and Drive while a man dressed as a crash test dummy stands on his head; and performing her single Hard straddling a neon pink tank – it fires puffs of smoke and T-shirts, clearly an early victim of defence cuts.
Over the course of the evening, they're also subjected to an awful lot of guitar solos, ranging in tone from wistful to widdly-woo. This is something no one comes to a Rihanna gig to see, in much the same way that no one buys tickets for Mark Knopfler in the hope that the former Dire Straits frontman is going to come onstage in a tuxedo, strip it off to reveal a basque, select a hapless male volunteer from the audience, then pretend to have it off with him.
Rihanna does all those things, but when she does, it's hard not to feel a degree of sympathy with Alan Graham: not because you agree with his view that the singer should "acquaint herself with a greater God", but just because there's something a little wearying about the relentless crotch-level bombardment.
Furthermore, there's also the sneaking suspicion that the more relentless it gets, the less interesting her music becomes, as if she's trying to divert your attention from her tendency towards the generic thumping house beats and rave synths that have engulfed the entire chart in recent years. You can sing it handcuffed to a pole while male dancers pretend to spank your bum if you want, but there's no getting around the fact that S&M is every bit as sexy as you might expect for a song about fetishism written by committee of five people – two of whom were previously responsible for the masterpiece of slow-burning eroticism that was S Club 7's S Club Party.
The annoying thing is that Rihanna doesn't need to make generic pop records: she already has a style of her own, melding her Caribbean roots with R&B. You can hear it on Man Down's swaggering fusion of reggae and hip hop, or on Hard, where her accent thickens. But if her material is of variable quality, the audience doesn't seem to notice. You can't really blame them. After all, Rihanna is sliding across the stage on a conveyor belt, dressed only in her bra and pants.
