just received the cadw magazine, it has an article about the Gwent Levels (a reclaimed coastal marsh area between Cardiff and Chepstow). Evocative photo of footprints discovered low down on the foreshore at Uskmouth: a woman and child walking in one direction passing a man's coming the other way, about 6,500 years ago. Other finds inc. bronze age oak trees and boats.
I haven't checked out the website yet:
http://www.selrc.dial.pipex.com