PASSERIFORMES: Passeridae
Passer domesticus
After it had left, I examined the fence post upon which I had seen a Brown Goshawk perched and eating a small bird.
Shining a torch down the hollow centre of the post revealed these House Sparrow chicks, and I suspected that a goshawk was now on the outside of one or both of their parents, which probably didn't bode well for the chicks' futures.
If you think these may be something other than House Sparrow chicks, please tap a few keys and let me know.