This course is not light on mathematics, so it is very important that you are slightly interested or at least tolerant of a fairly high standard of mathematics. In your first year you have to do at least a quarter of your course in mathematics, and another natural science subject. In theory there are several to choose from, but in practise nearly everyone does Physics. Physics is considered the hardest work of the first year - even though half your course is still Computer Science, you end up spending most time on the Physics