The BBC said Winehouse helped Ronson sing their 2007 hit "Valerie," but she seemed to forget many of the words to the song.
Winehouse, a Grammy Award winner, made the rare appearance during Ronson's first full performance with his new band, The Business International, at the 100 Club in London, the BBC said.
Winehouse's once-bright career has been eclipsed for some time by reports of her outrageous behavior, drug addiction and legal woes.
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