Who is Caius Porteus from Sarum: The Novel of England and what is their importance?

Caius Porteus is a young Roman officer in 60 AD. He is sent to serve in Britannica. When he criticizes his superior, he loses his fiancé, Lydia, and is sent to serve in Sorviodunum where he marries Maeve, the daughter of the chief Tosutigus. He realizes that he will never return to Rome and that his life in Sorviodunum and builds a Roman style villa on the estate. He and Maeve have two sons and a daughter.