Spoiler alert: this is the Matter of Britain as explored at the end of the Dark is Rising Sequence, the last few pages of Silver on the Tree.
All good things come to an end, and the narrative that begins (tentatively or with deliberate simplicity) with three children in a tussle over Arthurian legend in Over Sea Under Stone comes to a conclusion in a wild confusion of drowning cities, wounded kings, Welsh and English topography- and the three original children with their guardian, Merlin/Merriman, and his protégé Will facing off the Dark. Capital D, just as Will and Merriman and others are the Light.
What shocked and delighted me was the post-War humanism with which it concludes. Transcendence goes onto the ship with the previous guardians of the Matter of Britain, with Arthur “and all the hosts of the shades of Light.” Tir Nan Og, Tolkein’s Undying Lands, Aslan’s Country beckon, and the myths of Britain depart. It is a more dramatic rupture than in Tolkien or Lewis because of what follows:not Tolkien’s wistfulness or the hope of a new dawn in Lewis’ afterlife, but the rupture coming out of Auschwitz, of Hiroshima – and now the threats, ecological and military of our own time. The end of the matter becomes the start of a new struggle?
Bran, the boy who gives up his right to be part of the myth “stood watching until there was no ship to watch, but Will could see no regret on his face.” The charge laid on Will and the Drew children by the departing Merriman/Merlin is worth at the very least a tribute here: it is really worth reading the whole sequence of novels for, a humanist rabbit pulled from a transcendental hat:
“For remember…that it is altogether your world now. You and all the rest. We have delivered you from evil, but the evil that is inside men is at the last a matter for men to control. The responsibility and the hope and the promise are in your hands and the hands of the children of all men on this earth…
For Drake is no longer in his hammock, children, nor is Arthur somewhere sleeping, and you may not lie idly expecting the second coming of anybody now, because the world is yours and it is up to you. Now especially since man has the strength to destroy this world, it is the responsibility of man to keep it alive, in all its beauty and joy.”