Red Hot Chili Peppers, Portman Road stadium, Ipswich

The Red Hot Chili Peppers have become the biggest rock band of the past 15 years by brazenly embodying the form's traditional vices and virtues. Led by singer Anthony Kiedis, they have led a life of drug and sex-fuelled degradation in the underbelly of their native Los Angeles, leading to the early death of original guitarist Hillel Slovak.

Kiedis was schooled, as a Hollywood club kid, by watching Led Zeppelin in their 70s heyday and, like them, the Chili Peppers' dangerous appetite for life has enabled openhearted, muscular music. Mixing punk, funk, rap and classic rock with an unerring ear for the components of a killer single, they accidentally alchemised the sound that has defined post-Nirvana rock.

Having survived their excesses for a calmer middle age, they also now stand as knowing commentators on the decaying Californian dream.

Without ever compromising, they currently speak rock's international language more fluently than anyone.

Walking on in unatmospheric East Anglian sunlight, they promptly proved they haven't lost their touch with "Dani California", from their somewhat bloated new double album Stadium Arcadium. Kiedis bounds around stage, passionately clutching his microphone, while guitarist John Frusciante provides bluesy bottle-neck licks, over the talismanic Flea's bucking baselines. Another unkillable chorus, about a lost girl who seems to embody LA, had its kick off at Portman Road.

Flea, crop-haired in a psychedelic body suit, is soon making local friends, declaring Ipswich "the centre of the universe". Kiedis offers his sensitive side, on the soft relationship autopsy "Scar Tissue", it is charismatic merging of sensual bit-of-rough, musical idealist, rapper and rock crooner which the Chili Peppers spin around. But it's when the whole band bear down, as on the increasingly aggressive, countryish hoedown "Snow (Hay Oh)!" that the crowd really finds its voice.

Their new album's title track ascribes a sacred scent of ritual to stadium shows, and the Chili Peppers maintain an unusual sense of intimacy from their faraway stage.

When the bass riff from Clash classic "London Calling" leads into "Right On Time", it's one of several songs to show off their punk roots.

But it's with "Californication" that they really find their range. Kiedis conversationally outlines his vision of his medicated, sick yet golden state while Pop Art video images of busty blondes in big cars underline it.

The Ipswich crowd roar along. But when Flea's ominous base riff kicks out the start of "By The Way", as it finally gets dark enough for the crowd's massed mobile phones to shine as they lustily sing, everything ratchets up a further notch.

A riotous clattering of seats before the encore is rewarded by two songs from the Chili Pepper's defining 1991 classic, Blood Sugar Sex Magic. The heroin lament "Under The Bridge", introduced by a Frusciante riff as classically inevitable as an overture, pulses with the tension of a great, beloved song unfolding in front of us.

The double-time funk of "Give It Away'' then sees Kiedis handstand on the drums, and the others spin and jerk joyously. They are not done yet.