Who is Liam Delaney from Under the Jolly Roger: Being an Account of the Further Nautical Adventures of Jacky Faber and what is their importance?

Liam Delaney is Jacky's "sea dad." When she was very young on another ship and who takes over the duties as captain of the Emerald after Jacky takes that ship as a prize. Liam is stern but fair. He treats Jacky with deference because she owns the boat and he respects her abilities at sea but he also treats her more familiarly than most because of their history aboard another ship.