Unless things have changed recently, before getting accepted to one of the top universities in the UK you'll be expected to do an in-person interview.

(I remember having to choose one lecture to study beforehand and I chose Feynman's introduction to Special Relativity. I didn't even know who Feynman was at the time but really enjoyed his book of lectures, and a couple of years later he became one of my heroes after reading "Surely You're Joking Mr Feynman")