The Oxford Mathematics Christmas Public Lecture 2015 examined an aspect of Christmas not often considered: the mathematics. Delivered by Marcus du Sautoy, Simonyi Professor for the Public Understanding of Science. The Oxford Mathematics Christmas Lecture is generously sponsored by G-Research - Researching investment ideas to predict financial markets. Creative Commons Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales; http://creativecommons.org/licenses/by-nc-sa/2.0/uk/