Despite the fact that many people visiting the UK want to travel between the country’s most famous university towns, there are no direct trains from Cambridge to Oxford.
This means that the process of taking a train from one city to the other involves first travelling by train from Cambridge to London then travelling by train from London to Oxford.
Unfortunately, it gets even more complicated. Your first train will arrive at a different station than your second train will depart from, so it is not a smooth process. You will have to transfer stations using a bus, the tube, or a taxi, which is neither convenient nor does it guarantee that you will make your connection if there is traffic or if the tube is delayed.
As such, a much better way than taking a train from Cambridge to Oxford is taking a bus from Cambridge to Oxford. Buses are direct and do not require a change. The trip takes 3 hours and 20 minutes in total, and is far simpler than taking two different trains and changing train stations in London.