1) In the book Gems of Geometry, chapter 9 Relativity, the author wrote: "The General Theory concerns gravitation and the mathematics behind it is considered rather difficult ( post- graduate in these dumbed-down days I am sure ).
2) To get an idea of which mathematics books Alan Turing read during his studies I read Enigma by Andrew Hodges but the book did not answer that question. I even contacted Hodges by e-mail. He replied but he couldn't answer.
Question: How did the teaching of mathematics, at what we now call the Undergraduate Level, changed since the midth 19th century, ( when Riemann was studying ), until today? In topics and in depth and difficulty of the exams. Is it possible to reconstruct what Alan Turing likely had read when he started to write his paper on computable numbers? Is there any truth in John Barnes' remark "these dumbed-down days"?