Who is Sergeant Patrick Harper from Sharpe's Rifles: Richard Sharpe and the French Invasion of Galicia, January 1809 and what is their importance?

Sergeant Patrick Harper is described as a huge Irishman with a great sense of humor. He dislikes authority, and he is a natural leader, he is also extremely charismatic. Harper's character provides the perfect balance to the outwardly appearing rigid Richard Sharpe.