Elwin Ransom
Elwin Ransom may be based on C. S. Lewis' friend J. R. R. Tolkien ("Elwin" means "Elf friend" in Anglo-Saxon), though he seems to have autobiographical elements. In "That Hideous Strength" Ransom, with his royal charisma and matter-of-fact breezy acceptance of the supernatural, appears less like Tolkien than like Charles Williams (or some of the heroes in Williams' books).
William T. Kirkpatrick
William Thompson Kirkpatrick (10 January 1848 - 22 March 1921) was an Irish teacher and grammar school headmaster. He is best known for having been the tutor of the two Lewis brothers from Belfast, Warnie Lewis and C.S. Lewis. C.S. Lewis, who would later become well known as a literary critic, novelist, and Christian apologist, lived as a resident pupil with Kirkpatrick from 1914-1917. In his autobiography, Lewis reports that he was significantly influenced by his tutor.