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).
Robert Havard
Dr. Robert Emlyn Havard (1901–1985) was the physician of C.S. Lewis, his wife Joy Gresham and John Ronald Reuel Tolkien. Havard was a "skilled and prolific writer".