David Bowie made a surprise appearance on stage in London, performing two songs at a concert by Pink Floyd legend David Gilmour.
Bowie has rarely performed live since a heart operation in 2004
Bowie came on during the encore of Monday's show - the first of three sold-out gigs at the Royal Albert Hall.
The star received a standing ovation from fans before singing Pink Floyd's Arnold Layne and Comfortably Numb.
Bowie had heart surgery in June 2004 in the middle of a European tour and has since kept a relatively low profile.
The tour had already gained notoriety when Bowie was hit in the eye by a flying lollipop while on stage in Oslo, Norway.
Other special guests at Gilmour's concert included David Crosby and Graham Nash, formerly of the group Crosby, Stills, Nash and Young, plus singer-songwriter Robert Wyatt.
Gilmour's official website suggested there could be other surprises on the remaining nights, asking: "Who knows what new thrills await in the next two days?"