Interesting! I even considered the Dakota until you said that. Like others I thought British, but can't find that tail shape. Possibly from the USA then? Thinking Northrop in British colours? (see photo below) Gamma? Delta? 2E?
It is indeed a Gamma, in perhaps the only picture taken of one in WWII US military markings at, I kid you not, a top secret base, Project 19, in Ethiopia
I hate to say this, but that doesn't look like the YFM-1.
It looks more like an observer or bombadier position in the nose of a twin-engined aircraft. Also note the gear directly below. The maingear on the YFM-1 was rather tall and positioned foreward of center of each pusher-engined nacelle.