50 years ago this month -- June 5, 1975 -- Pink Floyd were in the studio working on a new song for the next album -- a long, epic song written in honour of their former leader and principal songwriter, Syd Barrett, who had been estranged from the band for years. And as they worked in the studio, they noticed an unfamiliar figure standing in the control room. To their shock, they suddenly realized that it was the very man the song was about, who somehow showed up that very day, uninvited. Randy Renaud revisits the bizarre tale of the recording of Shine On You Crazy Diamond for the latest edition of the Chronicles of Rock.