Just how good is Eric Clapton?

Eric Clapton turns 70 today. He has been acclaimed as a guitar hero since he first surfaced on the burgeoning London blues rock scene in the early Sixties with the Yardbirds and the Bluesbreakers.
 By 1967, an anonymous graffiti artist coined the phrase Clapton Is God.
He has been a global guitar legend for over fifty years. But just how good is he really?
Neil McCormick talks to experts to discover just how great a guitar player he really is.