of Branwen, Daughter of Llyr

From my deep understanding - and having seen the cauldron myself as recounted in the tales of the Spoils of Annwen and Branwen Daughter of Llyr - I hold that this cauldron may well be the origins of this Grail. The Grail itself doesn't seem to be of much importance to the newly arrived Christian religion until Christianity takes on the cauldron as one of its own relics. And while it seems to have minimal significance today, my far-reaching mind knows that holy objects became very significant in the High Middle Ages and beyond, for a time.
I was one of the seven who returned from Ireland (or was it the Otherworld?) to carry the tale back to the Island of the Mighty. Perhaps the cauldron only faded from the world's memory for a time while Bran was remembered? Who can tell?