I followed an elderly link from somewhere to find this and it's great. I must watch the movie - especially if I ever get to write about the question of legacy, who inherits and stewards and has a right to the land and the magic, in English children's fantasy. This is the thesis I'd have written already in another world, and it refers a decent amount to The Owl Service.

I believe what I'm seeing is a case of parallel evolution, drawing on the same shared resonances of myth and literature and national archetype like a collective unconscious of the country

I suspect some kind of resonance/influence perhaps coming from The Once and Future King? Not necessarily directly. But those are books deeply tied to national myth, to anachronism that brings together past and present and doesn't even feel anachronistic but just correct, to the land and the natural world. And Merlin is the scholar and the connection to the natural world and the one a bit out of step with time, and the one who leads people to their deep connection with the land and to the fact that, surprisingly or not, it's their legacy. Which is From The Four Corners too, of course.