A previously unreleased duet between??George Michael and Sir??Paul McCartney is to feature on a series of upcoming greatest-hits packages. George Michael's "Twenty Five" collections are scheduled to come out in November, in the form of two- and three-disc compilations.

Three new tracks will feature on the two-CD release, including the Macca track "Hear The Pain," plus "An Easier Affair" and "This Is Not Real Love" featuring Mutya, a former member of the Sugababes.

A fourth song, "Understand," will only come out on the three-CD compilation, while hits from across George Michael's Wham! and solo career make up each edition.

George Michael began a full European tour in Barcelona on Saturday, playing his first series of live shows in 15 years.