Rihanna, O2, London<br/>The Long Blondes, Amersham Arms, London

There's a scene in I'm Alan Partridge in which our hero is desperately pitching a new show to Tony Hayers, the head of BBC television, and starts reciting a list. "Shoestring. Taggart. Spender. Bergerac. Morse. What does that say to you about regional detective series?" Hayers, unconvinced, replies, "There's too many of them?" Alan, undaunted, counters, "Another way of looking at it is, 'People like them; let's make some more of them'."

The music business, at a macro-megabucks level, works in exactly the same way: people like Beyoncé Knowles, so let's make some more of her. After all, why throw corporate cash at a risky, off-the-wall speculation when it's so much easier and more lucrative to play safe?

Since Beyoncé can't be everywhere at once, there's a labour shortage for another black woman with marketably white facial features who can sing, dance and play the diva. This is the Rihanna-shaped gap, and the Barbadian 20-year-old fits it immaculately. Underneath the vast millennial canopy which, with the addition of a central column, would make the world's largest umber-ella-ella-ella, she looks the part, stepping out at the top of a long steel staircase wearing the little black number from that video, with boots, Posh Spice hair, and hoop earrings big enough to restrain a horse.

She's got the choreography and the showbiz shout-outs, punctuating the show with "Come on!" and "London, are you ready to party?". And her material hits all the right buttons. There's the acoustic pop-rock of "Hate That I Love You" (reminiscent of Sugababes or Pink's ventures in that vein). There's the strangely mournful dancefloor anthem "Don't Stop the Music" (incorporating Michael Jackson's faux-African "ma ma se, ma ma sa, ma ma coo sa" coda from "Wanna Be Startin' Somethin'").

There's sharp electronic pop in the form of the Soft Cell-sampling "SOS". There's the booty-bumping party-starter "Pon De Replay". There's the obligatory weepy ballad "Unfaithful" (mercifully free of Beyoncé-style histrionics). There's the space-filling cover version of Bob Marley's "Is This Love" (a slightly nauseating duet with the man himself on a screen). There's strutting retro disco in the form of "Break It Off". There's off-kilter pop in "Breakin' Dishes". (Cue a costume change into a PVC space vixen.)

Then, of course, there's "Umbrella", the song that conspired with the longest-raining, wettest summer since Noah's day to become the longest-reigning No 1 since Wet Wet Wet's day. It's an unlikely record-breaker, at first glance: it initially seems to have nothing to it, an un-song. But there's a certain something about it that's caused countless other acts (Manics, Linkin Park, McFly, Biffy Clyro, Starsailor) to cover it.

Inevitably, the dancers give it the full Gene Kelly. The crowd, however, does not, umbrellas having been banned from Rihanna's UK gigs after a spate of injuries at European shows. Rihanna does her job, executes her task with professionalism. So why does the whole experience leave me feeling slightly empty? Maybe it's just the weather-eather-eather.

In front of nicotine-stained lampshades and age-old Artex arcs, the campaign for one of 2008's key albums makes a low-key start. The Long Blondes' debut album Someone to Drive You Home was very broadly about being trapped in a doomed and destructive relationship with someone you loathe. Its successor, Couples, is very broadly about being back in the dating game, wondering if you can still cut it, and the regrettable behaviour that ensues: trying to make your ex jealous, nightclub encounters with unsuitable suitors. Hers is, as ever, the voice of experience: "I may never have a daughter cos I've far too much to tell her" is a particularly telling line.

This pub gig is the first chance to hear it publicly, and the new musical direction it heralds. Kate Jackson and her Sheffield quintet have made the inspired move of bringing in DJ Erol Alkan for his first full-length production job, and the results are wonderful. Alkan has highlighted the Blondes' disco-punk tendencies over their indie-pop instincts, and it matches Jackson's handsome voice – pitched perfectly between Chrissie and Debbie – beautifully. Indeed, she even drifts into a Donna Summer "Love to Love You Baby" falsetto on "Too Clever By Half".

But the fact that so many people like me are watching, rather than participating, makes this show strangely sterile. Furthermore, to make this a fine gig would have taken a little more than what we got, namely 45 minutes of the new stuff with "Lust in the Movies" and "Giddy Stratospheres" chucked in. Everyone's expecting a singles-packed encore; instead we hear Andrea True Connection's "More More More" over the PA, and faces fall. Would it really have killed them to come back out?