From shell shock in WWI to PTSD today many of those who made it home from war were left mentally scarred and traumatised. Historian Dan Snow explores the on-going mental health crisis in veterans.

In this one-off documentary, Dan Snow investigates PTSD, also known as shell shock, a devastating mental trauma experienced by soldiers from the First World War to Afghanistan, and how then, as now, the mental health services failed those who risked their lives in battle.—Tom Daly