"YOU guys wanted to be bigger than The Beatles, and I wanted you to be bigger than Chairman Mao, " lamented the Detroit-based White Panther activist John Sinclair after his protege band, the legendary MC5, decided they were musicians first and revolutionaries second, and flew the coop. He should have known better, but then the delirious late-1960s affair between rockers and revos . . . Leninists and Lennonistas . . . was passionate indeed while it lasted.

In the bubbling cauldron of the era of Vietnam and the civil rights movement, with Asian jungles and American cities both aflame, rock stars briefly seemed to be the cultural wing of an oppositional movement marked as much by generational lifestyle as by political ideology. Inspired by Bob Dylan, who had imported the folk world's tradition of topical leftist polemic into rock and then . . . on the principle of "first in, first out" . . . discarded protest in favour of his uniquely personal poetic voice, the performers at the sharp end of popular music did their best to address the complexities of the world in which they found themselves. The results ranged from Marvin Gaye's 'What's Going On' and James Brown's 'Say It Loud I'm Black And I'm Proud' to the The Rolling Stones' 'Street Fighting Man' and Jimi Hendrix's extraordinary deconstruction of 'The Star Spangled Banner'.

And yet, as Peter Doggett's exhaustive history of this doomed romance makes clear, it all went hideously wrong. The gap between the likes of Tariq Ali and Huey P Newton on the one hand and John Lennon and Mick Jagger on the other was simply too wide to be bridged, even by those who, like John Sinclair, Jerry Rubin and Abbie Hoffman, had made it their lives' work to do so. When Hoffman invaded the stage at Woodstock during The Who's set to deliver a speech about Sinclair's arrest for selling two joints to an FBI provocateur, and former Young Communist Pete Townshend swung a Gibson guitar at Hoffman's head and knocked him into the photo pit, the spray-paint was on the wall.

There are lessons to be learned here by both artists and the left.

Charles Shaar Murray Activists should never expect an artist either to provide a 10-point programme or to sign up for anybody else's, and should also realise that, no matter how eloquently artists might articulate the spirit of La Causa, their primary loyalties will always be to their muse and their comfort.

Artists should be aware that to politicos of whatever stripe or hue, they are little more than slot-machines: pop in a cause and wait for a useful chunk of agitprop to drop into the tray.

Furthermore, should the artist then step out of line, he or she will be denounced and persecuted to the maximum degree the politicos' resources permit.

In a sense, it was David Crosby who summed it up best.

"Somehow Sgt Pepper did not stop the Vietnam War. . . I am doing my level best as a saboteur of values, as an agent of change, but when it comes down to blood and gore in the streets, I'm taking off and going fishing."