Live: BBC Radio 1Xtra. Live.

Having brought the biggest names in the worlds of R&B, hip hop and UK G to both Coventry and Sheffield, names that've collectively scored more number one records than So Solid Crew once had members tonight the fringes of northwest London are treated to a slew of chart-clambering acts, both homegrown and transatlantic. Following the uniquely UK line up that graced the sticky stage of the Sheffield Arena 12 months ago, this year's BBC Radio 1Xtra Live is dominated by London's very own mixtape masters, backed by an ever so slightly slick smattering of American acts that get tonsils trembling to soaring pitches that are presumably audible well outside the M25.

With over half of London's tube lines struck down for the weekend, both Tinchy Stryder and Gyptian are unintentionally evaded, as an already infernal Wembley Arena witnesses Katy B continue her Magnetic Man-propelled operation for mainstream supremacy, as she belts out her latest explicitly excellent Benga-produced club annihilator Katy On A Mission over a backing track. However in the echoing hangar that is the Arena, lurking in the shadows of the Wembley ring Katie Brien's vocal chords sound strained as a lukewarm teabag, almost as flat as the dregs of an extortionate £4 Beck's Vier in the luminosity of the Americanised concourses tonight filled with ceaseless anticipation and the pronounced waft of Lynx. Sliding into the steely synths of Perfect Stranger, Katy B hardly looks dressed for the occasion, ambling about anxiously, before tonight's first clandestine guest turns out to be Ms. Dynamite in limb-clinging waxy leggings gyrating to the unlikely ladies' forthcoming single.

The first yank up on Wembley's whopping catwalk/stage hybrid is B.O.B., again relying as heavily on the backing track as Hayley Williams depends on fiery hair dye who tonight is rather unfortunately absent. Although having only encountered one another at a recent awards ceremony, it's hardly shocking... Bounding about in Kanye West-esque uproarious fashion, clunky hi tops and a lost Libertines jacket do little to claw a mucky take on Magic from the mundane, whilst Nothin' On You is a little more vivacious, if slightly vapid.

Far from jejune is Jason Derülo, whose laser fingernails and dainty tiptoes make for an insatiably extravagant show, hinging on Derülo's divine vocals and irresistible knack for carving an inescapable harmony from chart fodder. Bizarrely juxtaposing the Southampton suavity and absurd facial hair of Craig David with a Michael Jackson demure, Derülo tears T-shirts to raucous shrieks and slinks gracefully through the likes of Whatcha Say, In My Head and a roisterous Ridin' Solo, as instantaneously potent as three shots of sambuca swashbuckled behind your eyelids. Entirely insipid meanwhile is Labrinth, regarded primarily for his collaborative influx on the choruses of a certain someone currently roaming the wings with his JVC, as he wails over concurrent single Let The Sun Shine and dry ice swirls about a couple of backing dancers, before Simon Cowell's latest signing dives down the black hole side of stage. Dagenham MC with piercing, dagger-like lyrics Devlin follows, voraciously slashing through Brainwashed and its bone-splintering chorus, an eruptive Yasmin-featuring Runaway, before vanishing down the same gaping orifice as Labrinth. Fighting his corner, indeed...

Incendiary and indubitably intelligent is Tinie Tempah who despite Labrinth's inexplicable absence quite literally incinerates the Arena, as flamethrowers interrupt an interminably boisterous Frisky and hefty, eardrum-crunching six-string distortion. Equally flammable is the consonant-based club smash collaboration with Swedish House Mafia, Miami 2 Ibiza, tonight sounding as sizeable as the States, before segueing into a sidereal Written In The Stars and a devastatingly exuberant Pass Out. Expect copious women, cars, cards and glasses when Tinie tours the great British Isles rather shortly.

Less celebratory is tonight's star, well, stud-studded special guest Cee Lo Green, tonight costumed as a plus-size racketeer, accompanied by leather-clad miming guitarist. Fuck You does however sound as disposably indulgent as an afternoon in Atlanta, Georgia's most calorific swivel-seat diner. More cacophonous than cholesterol-elevating are E14 grime-turned-gumball R&B collective Roll Deep, whose excessive numbers and generic choruses are all too trashy and self-satisfied to invoke much sensation, Green Light sounding akin to Maths + English-era Dizzee rammed down Aqua's esophagus.

And so to NW1 behemoths N-Dubz, Tulisa, Fazer and Dappy bustling onstage to the Against All Odds intro, before bursting into a perky I Need You. Woolly hat obsession, joviality and enough ticker tape to aliment a Flaming Lips world tour convert the Camden trio into true headliner material: from the plonky keys and AK47 rap and rhyme of Say It's Over to bona fide greatest hit of sorts Strong Again, to the wonky balladry of Playing With Fire, from humble beginnings aka "practically nothing", the thousands screaming their name continue to swell exponentially, despite forthcoming single Best Behaviour sounding as limp as Dappy's droopy old beanie looks. Trademark Na Na incurs excessive tongue rolling and an unfathomably Tinchy Stryder-less Number 1 is serotonin set to the BPM of an Oceana DJ database, as BBC Radio 1Xtra Live establishes itself as the quintessence of R&B repayment for oft-warranted millions of Youtube views and iTunes-induced revenues.