Who is Clarke from Commodore Hornblower and what is their importance?

Clarke is an Englishman who, for unknown reasons, has cast his lot with the French. He is put aboard Maggie Jones, a captured English merchant ship, as the captain of a prize crew. When he meets Hornblower's Baltic flotilla, he closes and attempts a ruse to escape recapture. He tells Hornblower his ship is infected with smallpox. Hornblower, however, sees through the ruse and orders the merchant ship be boarded. When the first boarders gain the deck, Clarke, in desperation, shoots himself in the head, shattering his lower jaw. Although the shot is not instantly fatal, it is a mortal wound. After lingering for a few hours in delirium, he dies.