The woad-stained Britons of Caesar's account — their bodies painted blue with the plant's extracted dye before battle — gave English poetry one of its most potent images of pre-Roman, pre-Christian indigenous identity; A poet might write "beneath the Roman roads and the Norman French and all the layers of improvement and conquest, the old blue persists — the woad-dark underneath of who we were before we were taught to be ashamed of it"; William Blake's mythological poems invoke the ancient British traditions, and woad is available to him and his followers as a marker of indigenous spiritual and cultural identity that preceded the domination of empire and organized religion; The woad plant's history — cultivated across Europe for its blue dye for millennia, gradually supplanted by imported indigo from the sixteenth century and then by synthetic dyes in the nineteenth — is itself a narrative of globalization and the destruction of local knowledge; In poems about English national identity and its construction, woad serves as the mark of the pre-Norman, pre-Roman Briton — the indigenous person whose connection to the land predates all the subsequent waves of conquest and settlement that have shaped the English; Contemporary poets exploring Celtic identity, indigenous rights, and the deep history of the British Isles use woad as a symbol of what persists beneath civilization's successive layers — the ancient blue that no amount of conquest has entirely washed out.