Led Zeppelin, The O2, London

With the possible exceptions of The Beatles and Pink Floyd, no other band reunion could excite the fervour prompted by Led Zeppelin's long-awaited appearance at the O2, particularly since Cream buried their various hatchets a few years ago.

Certainly, it's hard to imagine any other act charging a whopping 135 for a ticket, and still being so over-subscribed with requests that they have to run a lottery to choose which lucky blighters will have the opportunity to part with such a princely sum for an evening's entertainment.

Expectations would already be high whatever the price, but that kind of outlay raises the bar to even more vertiginous heights although there is a point at which the cost virtually ensures satisfaction.

It's like the adage about being in debt: if you owe the bank 10,000, you have a problem; but if you owe them 10,000,000, the bank has a problem. Likewise in this case, if you've paid 135, you have more of a vested interest in believing you've had a great time than if you'd only paid 20 or 40.

So although the terms "awesome" and "brilliant" could be heard amongst the departing throng following Zeppelin's first full-length concert since John Bonham's death in 1980, they were perhaps more an inevitable self affirmation than a considered judgment on the show itself which like all performances, had its highs and its lows.

The event was billed as a tribute concert to Atlantic Records founder Ahmet Ertegun, a beloved friend and mentor to the band. I don't know how much the 20,000 audience knew or cared about Ertegun's career and his position in American music history, but it certainly struck me as strange, for a man who was so crucially involved in the development and promotion of black music in all its forms, from jazz and blues to soul, that there was no black presence on the bill.

There were plenty of musicians heavily influenced by black music, certainly, but this merely served to remind one of the accusations of plagiarism levelled early in their career by Led Zeppelin's light-fingered (and often uncredited) appropriation of blues material originally written by the likes of Willie Dixon.

Tonight at least, Robert Plant is at pains to give due credit to the originators, acknowledging the roots of "Trampled Underfoot" in Robert Johnson's "Terraplane Blues", and giving props to Blind WillieJohnson as author of "Nobody's Fault But Mine".

But the white-blues bias did tend to overbalance the concert as a whole. And frankly, if the main course is as dense and heavy as Led Zeppelin, the last thing one needs is a starter as rich and stodgy as Bill Wyman's Rhythm Kings. Unless it's Foreigner, the epitome of redundant '80s stadium-rock.

Zeppelin's headline segment opened with quaint period newsreel footage of them arriving in America in their heyday, before the familiar chords of "Good Times, Bad Times" heralded their appearance. Here, and on the subsequent "Ramble On", it became immediately apparent that Jason Bonham makes a more than merely able replacement for his father on drums: indeed, there's a stronger funk element to his playing which kicks the songs along with more elan, particularly on "Trampled Underfoot", where it lays a tight bed beneath John Paul Jones's funky clavinet riff.

The sound early in the show was somewhat murky and billowing, at times an undifferentiated clangour through which Jimmy Page's piercing guitar solos cut like razors. But by "Black Dog", things have settled down somewhat, the riff's tricky curlicues coming through more clearly; and Robert Plant's call-and-response jousting with the crowd on the "uhh-uhh/uhh-uhh" mid-song breakdown is one ofthe night's more engaging moments.

It's followed by the blowsy slide-guitar blues "In My Time Of Dying", on which Page's climactic blizzard of notes seems to congeal like molten lead. That in turn is succeeded by "For Your Life", the most-puzzling piece in the set. "This is our first live adventure with this song," says Plant in his introduction and no wonder, one thinks, listening to this routine riff-a-rama whose melody remains a mystery.

"Trampled Underfoot" is a distinct improvement, but its impact is immediately dissipated by a lengthy section of downbeat blues-rock, starting with "Nobody's Fault But Mine" and incorporating "Since I've Been Loving You" and "Dazed And Confused" cue Page's employment of violin bow to send wavesof lowing noise careering around the arena, Plant moaning along in unison with only the heavily vibrato'd keyboard and vocals of "No Quarter" as respite.

Which, being the closest the band came to the dread jazz-rock fusion, is no respite at all, to be honest. It all seems rather sluggish and draggy, an impression not dispelled when Page straps on his emblematic double-necked guitar for "Stairway To Heaven", scourge of guitarshop salesfolk the world over.

The evening's high point comes with the mighty "Kashmir", whose middle-eastern-toned riff has a golem tread which makes it the song best equipped to withstand the arena's questionable acoustics. It's also given the most satisfying of the visual backdrops on the huge screen behind the band, a complex series of mandala devices which brings out the song's exotic flavour.

"There are people out there from 50 countries!" marvels Plant in his introduction. "This is the 51st."Encores of "Whole Lotta Love" and "Rock And Roll" bring the evening to a close, the former given the full-on laser and dry-ice treatment for Page's celebrated mid-song breakdown section of guitar and theremin.

One can't help feeling, however, that these big, uptempo rockers would have been better placed in the middle of the set. But for those happy punters departing Greenwich in a state of mild euphoria, just to be here was clearly enough.