i was rereading Stanley Booth's biography of Keith last night. Stanley was friends with both Gram and Keith, and he spends a page or so debunking the myth that Gram contributed to Wild Horses. he attributes the music, the title and the lyrics of the refrain to Keith, and the rest of the lyrics to Mick; he says Gram's role was simply loving it enough to want to record it.
the myth could easily have arisen simply because Gram recorded the song. after all, there are people who believe Chuck Berry wrote Down the Road Apiece, even that Otis Redding wrote Satisfaction.
"What do you want - what?!"
- Keith