Canterbury City

By Rail Trains run frequently from London to Canterbury East or West, and both stations have busy taxi ranks for the 10-15 minute journey to the ground.
If there are 3 or more or you and you travel together then you can also get ⅓ off by using GroupSave.
Southeastern also run high-speed trains from St Pancras to Canterbury West (via Stratford), though these are more expensive - and make sure you board in the front carriages, as the platform at Canterbury West is too short for the full high-speed trains.