In an occasional revival of the classic television interview format, Jeremy Isaacs talks to Merce Cunningham. At the age of 70, Cunningham is perhaps the world's best-known choreographer of modern dance. Since 1953, when he founded his own company, he has been at the forefront of modern experimentation. Cunningham talks about the motivation behind his unflagging creative energy, and his collaborations with artists such as John Cage , Robert Rauschenberg and Andy Warhol.