Film-maker Scott Cooper describes how his small role in a civil war drama starring Duvall led to a happy, lifelong friendship with the great actor, who died earlier this week

I first met Robert Duvall in a muddy field in Maryland in 2001, on the set of Gods and Generals. It was a Warner Bros civil war epic, the kind of production where the scale alone made you feel small. I was playing a low-ranking Confederate aide-de-camp to General Stonewall Jackson. I was young, unsure of myself, and painfully aware of exactly where I stood in the hierarchy of things.

That morning, they placed him on the horse.