Paleolithic flint hand axe, found at Northfleet, Kent. The chalk around Swanscombe, Ebbsfleet and Northfleet has yielded a highly significant array of archaeological treasures, of which this is but one example. The period, starting about 3.3 million years ago, and ending about 11,500 years ago, was in large part characterised by the production of hand tools from stone, flint being particularly prized for the sharp cutting edges that it could hold.