How we remember the dead, and why does it matter? In this special edition of The Why Factor Mike Williams starts with the promise of so many nations never to forget the death and suffering of the First World War, to explore how the dead have been remembered around the world and through the ages.

Produced by Ben Crighton

(Image: Ceramic poppies covered in rainwater at the Blood Swept Lands and Seas of Red evolving art installation at the Tower of London Credit: Chris Jackson/PA Wire)