Lady Barbara Wellesley was Horatio Hornblower's second wife. She first encountered Hornblower in Central America, where she requested passage aboard the HMS Lydia to England. As she was the sister of Arthur Wellesley, Hornblower was obliged to provide her with passage, along with her servant, Hebe.
On the long voyage, he and Lady Barbara became strongly attracted to each other. Nearing the end of their trip, she made the first overt advances; Hornblower demurred, explaining that he is married. Also, as a man of humble social standing, he could not afford to risk offending the influential Wellesley clan by dallying with her. After the rejection, the embarrassed Lady Barbara avoided him as best she could. Fortunately, an English convoy was sighted soon afterwards and she transferred to a more spacious ship. They made stilted, formal good-byes.
After Hornblower's escape from French captivity, he discovered that his first wife Maria had died in childbirth and that his infant son had been adopted and was being cared for by Lady Barbara. As she had been widowed by the death of her husband, Hornblower's former commander, Admiral Percy Leighton, they were free (after a decent interval) to marry. Barbara is more beautiful, cleverer and far richer than the poor Maria (whom Hornblower had more pitied than loved). Thereafter, he lived (uncomfortably) as a country squire in Smallbridge, Kent.
During Hornblower's posting Commander in Chief of the West Indies Station, Lady Barbara comes out to Jamaica for Hornblower's final days in post, and to accompany him home. On the voyage back, they endured a hurricane and shipwreck. Near death, Barbara dropped her final wall of reserve as she assured him she had never loved another man.