Killed on a Quiet Day in the Trenches

In this episode we discover the tragic stories of 2 soldiers, one from London and one from Australia, who both died from the effects of German trench mortar fire. But not during a famous battle. These were incidents that happened during a quiet period in the trenches. What happened to them? Lance Corporal Thomas Stevenson from New South Wales had been wounded and buried by shellfire at Fromelles but survived, only to die near Messines a year later. And Alf Stevenson from London died of gas poisoning on the Somme. But how?