Where are good areas to go cycling not too far from London?

Question

I live in London but would like to get out to the countryside to with my newly acquired mountain bike. I'm not an overly strong cycler and am after more of an easy day ride than anything too strenuous, and needs to be able to be reachable by train as we don't have a car. Any suggestions for areas within a couple of hours of London?

Answer 1

North and South Downs (Surrey/Sussex).  Catch a train from either Waterloo or Victoria to somewhere like Dorking or Epsom.  Plenty of good stuff there.