Matthew Waterhouse

He plays a student named Briarly and has a very affecting scene towards the end of the first episode. After Briarly has been informed by the headmaster's wife that his father died in battle (this is 1918, toward the tail end of WWI), new faculty member David Powlett-Jones (a survivor of the trenches) goes to speak to him. They talk briefly about how the death of Briarly's father will affect the boy and his family, and what it means to be "killed in action." He also appears in a few other short scenes with other schoolboys in the first and second episodes of the series.