This day forty years ago Led Zepplin's landmark album 'Physical Graffiti' was released.

To discuss the signicicance of this seminal record, Tom Dunne was joined by Mick Wall on Tuesday night, the author of 'When Giants Walked the Earth', the definitive biography of Led Zepplin.

Wall explained that this album represented the pinnacle of the band's output.

"Physical Graffiti is everything they stood for and tried to achieve," he said. "But also the moment that Rome started to fall".

After this landmark album, Wall feels that Led Zeppelin became victims of a number of debilitating factors, not least the advent of punk.

Tracks from the album, such as Kashmir, remain classics to this day. The album has been remastered and reissued for the anniversary.

To listen to the full interview, simply click on the above link.