English: "The ancient Briton had no fleet, whilst the hardy Norseman was, at that time, practically master of the sea. If, on land, they met with a repulse or temporary defeat, they could take to their boats and summon to their aid the reinforcements that were continually arriving on the south side of the Island, and return with redoubled force and vigour to the onslaught of their objective. If plunder were their immediate object, the idea, accord­ing to local tradition, seems to have originated in the fact that the County of Essex was reputed to be rich in mineral wealth ; and that, round its coast, more especially that portion immediately abutting the Thames, or the Tamis as it was then called, from Tilbury to Shoeburyness, an abundance of gold and silver was to be found. This, therefore, has been supposed by some to have been the initial attraction of the Danish invaders. How far this theory is true we cannot vouch; but there remains the fact that we have numerous references to the existence of King Conubelin’s gold mines in this vicinity, in ancient records and subsequent histories...

"Some remains of these alleged Conubelin gold mines are yet to be seen between Benfleet and Tilbury, now called “Dene Holes” or “Danes Holes,” and vary from sixty to seventy feet in depth. They were evidently in a good state of preservation in 1610, inasmuch as Camden, who personally inspected them, not only makes mention of them in his Britannia;, but also furnishes us with the quaint illustration we have taken the liberty to reproduce on the opposite page. Camden’s description of them is almost as quaint as the illustration. He says: ” Neer untoe Tilbury, there be certaine holes in the rising of the chalkey hills sunke intoe the ground tenne fathom deepe, the mouth wherof is but narrow, made of stone cunningly wrought, but within they are large and spacious. Tradition hath it that they be some of King Conubelin’s golde mines.”

Deneholes were in fact primarily for the mining of chalk, especially for use in agriculture.