Who is Captain Bolton from Ship of the Line and what is their importance?

Captain Bolton is the commander of the Caligula, one of the three ships in Leighton's squadron. He is described as a large, heavyset, coarse man,who is much given to bawdy humor, heavy eating, and liberal drinking. When he began his naval career, he was nothing more than a common seaman. His exceptional ability, however, allowed for his rise in the ranks.