Red Hot Chili Peppers, Koko

I'm not quite sure why Anthony Kiedis bothered to put on his multicoloured frock coat. It certainly wasn't to keep warm. The atmosphere in Koko was positively volcanic even before the Red Hot Chili Peppers appeared on stage at this exclusive Radio 1 showcase. Highlights are due to be broadcast during Zane Lowe's show on 12 September from 7pm to 9pm, but a radio airing will convey only a miniscule fraction of the zip of this age-defying band.

This gig was intended to promote the new album I'm With You, but they also did a pretty canny job of mixing old crowd-pleasers with new tracks. As soon as the band had rattled through the opener "Monarchy of Roses” Kiedis whipped off his coat, revealing his tattoo-festooned torso. There were some initial niggles, though. The vocals were not quite crisp enough and, well, let's not beat around the bush, or rather the 'tache, Anthony Kiedis's current facial hair is not quite right. He might be trying to rock a Nick Cave-meets-Zapata look, but from the balcony it was more like something furry was sheltering under his nose. There was no faulting the singer’s energy though, as he leapt around, cut shapes in the air with his palms or clutched the microphone with an arresting sense of urgency.

And as for the music, the 90-minute gig quickly improved. The frenetic second track was a pure classic. "Can't Stop" won over the diehard funk-rock fans while showing the breadth of the band's style by morphing into a reggae jam towards the end. The new number "Ethiopia" was similarly eclectic, mixing loose-limbed pop fizz with a freestyle jazz noodling vibe. Overall I'm With You feels a little like playing safe after 2006's turbo-charged Stadium Arcadium, but for a band who once released an album called Blood Sugar Sex Magik it would be unfair to call this release Mortgage Payment Protection Insurance.

The oldest three band members are parents – at one point Kiedis took a breather to dance with his young child in the wings – but on stage they are the kids. Like the equally evergreen Beastie Boys, the Chili Peppers know how to have fun. They've come a long way in three decades and may have grown up in some respects – they once wore socks on their genitals, they now probably wear them on their feet to avoid deep vein thrombosis – but they can still rock the heck out of a room. A positively demented cover of Neil Young's "Everybody Knows This is Nowhere" was described as "fun as fuck" by bassist Flea.

Denim-clad Will Ferrell lookalike Chad Smith was on fearsome form, pounding out a thunderous drumbeat on the standout new track "The Adventures of Rain Dance Maggie", a sentimental, romantic anthem which comes complete with cowbells, syncopated rhythms and a guitar motif from well-behaved new boy Josh Klinghoffer, replacing John Frusciante, that has pleasing echoes of George Harrison in it.

But if Kiedis, Smith and Klinghoffer did their bit to make a night of it, it was that oldest punk on the block, 48-year-old Flea, who dominated the small stage, bouncing around like a topless teenager full of Sunny Delight. His playful runs underpinned new tracks such as "Factory of Faith" that mashed up pop metal with a rap sensibility. It was the older songs that inevitably grabbed the attention though. "Californication" had the floorboards in the stalls springing up and down from Klinghoffer's first strummed chord, "By the Way" closed the set in style, while a primal, charged encore of "Give it Away" prompted the largest, loudest singalong of the night.

If songs from the last decade prompted the most enthusiasm from the hardcore fans, my mind occasionally drifted back further. Leaning against the balcony railing I realised I stood in exactly the same spot to watch The Clash here 32 years ago, when the venue was called The Music Machine. Nothing is ever going to match the only-young-once febrile thrill of seeing Mick Jones and co in full, ferocious flight, but there were moments on Friday evening when the Red Hot Chili Peppers were not far off.

• Find I'm With You on Amazon

Watch Red Hot Chili Peppers perform "The Adventures of Rain Dance Maggie"