Oh! Steady on! Let's not give our American friends the laurels to soon, though I wish they had kept at least one of those fabulous "wings".
How about the Westland Pterodactyl series which the late great Harald Penrose tested extensively in the '30s, way way before those Northrop jets. Incidentally pitch stability was their eventual downfall too, though the design's potential was clearly demonstrated. See Harald's many books for the whole story.
Am I right in thinking that some of the Horten machines are still in the Smithsonian reserve collection gathering dust?