It doesn't have a very good write up on Wiki ...maybe that's why you don't remember it
"Hatter's Castle" was shown on BBC One on a Sunday afternoon as one of their Film Matinees. I saw quite a number of them with my parents and my brother.
The following week they had "The Red House", the Edward G Robinson film I mentioned some time ago, I assume I saw it then but didn't recall it when I watched it again a year or so ago.
The previous week they showed "Sullivan's Travels" (1941). I do remember watching it then and I've seen it a couple of times since. Joel McCrae and Veronica Lake starred, and it was directed by Preston Sturges. Hollywood film director decides to experience life as a homeless person to see what it's like as part of his preparation for his next film. A superb film which starts off as a comedy but a serious powerful drama by the end. Rated as the 40th best film ever made in Halliwell's top 1000.