Just a snippet from History, Gazetteer and Directory of Norfolk.. by William White (3rd ed, 1864):
At the side of the road, near the boundary of Stockton and Hales, is a large stone, weighing about two tons, called “Stockton Stone,” and in the ancient Town Book, still preserved, is an entry, dated 1645, recording the payment of a small sum for “putting stulps to Stockton Stone.”
A stulp is a support or post. So it sounds like they were looking after it.