Who is Randolph Henry Ash from Possession: A Romance and what is their importance?

Randolph Henry Ash is a famous Victorian Poet. He has dark brown, almost black hair, and rough, black brows. He dresses elegantly but not extravagantly. Randolph wrote the letters that Roland discovers years later in the London Library. Randolph has a reputation as a dedicated and loving husband. He actually has a turbulent affair with a poet named Christabel LaMotte which results in an illegitimate child that is ultimately raised by his lover's sister. He meets the child once in his life and realizes sadly that she is his own.