Okay, here is what my contact Philip has said: "That is a good one. It is a real typical raptor feather. Lots of species have quite similar colours. To be 100% sure one would need to compare it to known specimens. However I’m confident it is from a Brown Falcon. I believe that is the only contender that shows the little orange patches and especially spots, in addition to the fairly basic brown & white bar patterns. I think an inner secondary feather."