Roger Taylor, in an interview for the BBC documentary Queen: the Days of Our Lives, stated that Deacon had indeed created the bassline, stating that all through the sessions in the studio he had been playing the riff over and over; he also claims that when the band returned from dinner Deacon had, amusingly, forgotten the riff, but fortunately Taylor was still able to remember it http://en.wikipedia.org/wiki/Under_Pressure
@Metality: _"Vanilla Ice rip-off" _ You do know this song was recorded a DECADE before Vanilla Ice made his record, don't you? And that Vanilla Ice actually ripped off David Bowie/Queen, right? Yeah, I didn't think you knew. Actually helps to know what you're talking about before spouting off.