Who is Lieutenant Freeman from Lord Hornblower and what is their importance?

Lieutenant Freeman is the captain of Porta Coeli. He is described as square, stocky, and swarthy. Freeman wears his dark hair long and in ringlets, belying his part-Gypsy heritage. He is reputed to be a capable captain, and he is intimately familiar with the channel coastal waters. Hornblower relies heavily upon Freeman's seamanship.