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).
Joy Davidman
Davidman had become interested in C. S. Lewis while still in America. She first met him in August 1952, when she made a trip to the United Kingdom, after a two-year correspondence with him. She planned to finish her book on the Ten Commandments that she had been working on, and which showed influences of Lewis's style of apologetics. After several lunch meetings and walks accompanying Davidman and his brother, Warren Lewis wrote in his diary that "a rapid friendship" had developed between his younger brother and Davidman, whom he described as "a Christian convert of Jewish race, medium height, good figure, horn rimmed specs, quite extraordinarily uninhibited." She spent Christmas and a fortnight at The Kilns with the brothers. Though Davidman was deeply in love with Lewis there was no reciprocation on his side.