What was the name of C.S. Lewis's tutor in English literature who later became a major influence?

William Kirkpatrick was C.S. Lewis's tutor in English literature before Oxford.

William T. Kirkpatrick, whom Lewis called “the Great Knock,” tutored Lewis privately in preparation for university examinations. Kirkpatrick was a rigorous teacher known for demanding precise reasoning and sustained debate. Lewis later remembered the training as intellectually formidable and influential in the development of his argumentative habits.

Lewis studied with Kirkpatrick at Great Bookham in Surrey after leaving school and before entering Oxford. This period helped prepare him for the scholarship examination that led to his university education. Kirkpatrick's methods differed from the literary friendships Lewis later formed with Owen Barfield and J.R.R. Tolkien.

Because Barfield and Tolkien became famous members of Lewis's intellectual circle, they are sometimes mistaken for his earliest formal tutors. Kirkpatrick, however, held that specific preparatory role. Lewis's autobiography, Surprised by Joy, provides an important account of the demanding education he received from “the Great Knock.”