It's almost impossible to say why this works. Made in 1974 for the BBC's Play for Today strand (one of those things the BBC is proud to have done but would run a mile from doing these days), it is equally impossible to describe in terms of either plot or narrative. It's perhaps a series of dreams, images and experiences seen through the eyes of a young boy growing up in rural England. Chuck in homoerotic fantasy, discussions with Elgar, Christian and pagan ritual and a dead bird (...and some other things which I won't even list because you'll find yourself waiting for them to turn up) you start to get the sense that this is something simply to experience rather than describe.
The play has an almost legendary status because of its elusive and layered qualities, raising the concern that, like the last episode of The Prisoner, it may actually be beautifully crafted nonsense and not worth sticking with. But be patient: this was directed by Alan Clarke one of the best TV directors Britain ever produced. While he is reputed to have said he didn't understand the play either, he nevertheless manages to pull out the various themes within the piece and weave them together create a genuine sense of enigma rather than mere confusion or tacky suspense.
By the time you reach the final scenes you may have the feeling of having glimpsed something rather than actually seen it. For that alone, it's an experience worth having.
Also worth having is a "what the fuck was that about?" discussion afterwards in which you attempt to describe what it is you've just watched.
There will be a lot about Play for Today on here. It's inevitable.