When he started out, Lenny Kravitz was a quirky singer-songwriter with a yen for 1960s production techniques and borrowing the best bits from classic rock and soul. Somewhere along the line, he developed into a full-blown arena-rocker, and the changes have not been for the better.

This solitary Wembley date began in spectacular fashion. The stage curtain fell as the band ripped into Where Are We Runnin'?, revealing Kravitz gyrating at the microphone in sunglasses, Huggy Bear woolly hat and a vest that looked like the remnants of an old fishing net. The song was a fat, funky thing, and Lenny, flanked by his sizable band - three singers, three brass players, plus the usual bass, drums and keyboards - supplied the solo on his Flying V guitar before handing the instrument to a compliant roadie. Funkier still was Always on the Run, where Kravitz, re-armed with a gold-top Les Paul, led from the front by pumping out the dirty, lowdown riff.

It was at this point that Kravitz suddenly began to succumb to Big Rock disease. He started shouting things like: "If you're feeling good, say all right!" And then there was an embarrassing interlude where he wanted to play a solo on the bass, only to find the bass wouldn't work. Not to be upstaged by a mere technical failure, Kravitz kept the band idling in the background for an aeon as he yelled "Somebody bring me a motherfuckin' bass!" before the fault was eventually ironed out.

After breezy performances of his new single, California, and the tie-dyed Fields of Joy, Len went pear-shaped again, turning Fear into an extended jazzy interlude in which everybody got a chance to solo and Kravitz displayed his prowess on drums. He could have played about three extra songs instead, or four if he had dumped his cloth-eared version of American Woman, which lumbered along like Queen's We Will Rock You. Not his finest hour.

· At Party in the Park, London W1, on Sunday. Box office: 0870 060 1757.