The scar clearly seen below Sean Bean's left eyebrow is real. It was given to him by Harrison Ford who accidentally hit him in the face with a boat hook during filming of Patriot Games (1992).
The character Pvt. Daniel Deever (Charles Venn) dies a heroic death, but it is just after he commits an act of cowardice -- abandoning his post and comrades in the face of the enemy. In 1890, Rudyard Kipling penned the poem "Danny Deever" about the execution of a British soldier for murder. To "do a Danny Deever" is archaic slang for committing a hanging offense; cowardice is among those offenses.
This was the final project made by director Tom Clegg before his death in 2016. He directed every single episode of Sharpe (1993), which is unusual for a multi-year series.
This episode takes place in 1818.