A day trip to Rochester by train costs less than 20 pounds return, and takes you away from the noise and smells of London to the tranquility of the Medway towns. All of the attractions mentioned above are easily reachable by walking from Rochester, but if you are unable to walk far then public transport options are available.
If you have the time it really is well worth spending a couple of days to explore this area steeped in over a thousand years of history. Just exploring Rochester Castle alone will take a morning, so trying to squeeze all the places into one day isn't really a good option.
Budget accommodation is available in the area, but book ahead if you plan to stay to avoid disappointment.
Upon reaching Rochester, there is an attractive colourful town to explore, with good eating and shopping facilities. In the shadow of imposing Rochester Castle you will find plenty of interesting sights to see.
You can walk to Upnor Castle (about 3 miles) in around an hour and absorb some of the local atmosphere and sights of the river. Or if you would prefer to save your energy, you can take a 197 bus from Monday to Saturday. Be sure to check the timetable before you set out though.
This great example of an Elizabethan fort is fascinating if you have an interest in military or maritime matters.