This enclosure is one of several uncovered in the last couple of weeks.
It is 5m x 5m, surrounded by an uninterupted ditch which is a u profile 1m wide at the top and at least .5m deep. The lack of an apparent entrance is interesting.
Tarmac have stepped up the pace of archaeological destruction, these are being bulldozed within days of being recorded.
http://www.smartgroups.com/pictures/openalbum.cfm?GID=2022706&AlbumID=4007561