This flew past me at about eye level (barely observing the required 2m social distancing) and my impression was that it was around the size of a collared dove. It seemed too small to be a sparrowhawk (although my experience of them is limited). Is it a merlin? (My experience of them is nil.)
I had been watching some gulls see off a hen harrier, and just turned back to resume my walk as this flew across the path in front of me, then turned and flew past on my right. I barely had time to register more than "That's a raptor!" before it was past, but then it helpfully perched on the other side of the road and let me walk back to get photos.