I.: Origin of Obligation to make Bridges.

The Norman kings seem to have based their claim to compel their subjects to maintain bridges upon the ancient tripartite obligation (known as the trinoda necessitas). Three duties were required of all the men of England in the interests of the commonweal: attendance on the fyrd or local militia; the making of roads, so necessary for military purposes; and the repairing of bridges and fortifications. Gradually, as feudal tendencies prevailed, the obligation to construct bridges ceased to be a personal burden upon all freemen, and became a territorial burden. The present chapter seems to be a particular application of the general principle enunciated in chapter 16. “Brigbot” required special treatment because of the prominence into which it had been forced by John.