Well the thing that keeps being forgotten about Oxford and Cambridge is that cycling has a significant modal share of journeys to work, i.e. it is an important mode for journeys made by local people, not just students. Furthermore, as others have pointed out, there are plenty of places with lots of students and low levels of cycling. A large student population is not a 'necessary and sufficient' condition for high levels of cycling; nor is being 'flat' (btw PK99- have you seen Headington hill in Oxford?). Nor is having lots of 'cycle routes'. More important in the case of Oxford and Cambridge is a lack of car parking and the generally traffic constrained nature of the road network making cycling advantageous over driving; and that is the reason why cycling is taking off in London, as well.