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).
Francis Turner (RAF officer)
Turner returned to Magdalene, eventually becoming Pepys Librarian and President of the College. His contemporaries included Dennis Babbage and C. S. Lewis, and he became a close friend of T. S. Eliot.