Sundial – Gonville and Caius College, Cambridge

Gonville and Caius College – the fourth oldest college in Cambridge (Estd: 1348) has a very interesting six-sided sundial on one of the gates. The exact time I took this picture was 1:54PM GMT, and interestingly the sundial shows a time that is just an hour off.
Is this due to difference in local and GMT? Or was I looking at the wrong sundial? A later visit may answer that question.