Were there other birds in sight, and if so, how where they behaving? If
in a very troubled manner, then your bird may have been a sparrowhawk.
Yes, sparrowhawk is one of the strong possibilities I came up with.
I was in the garden which is pretty much a square enclosed by buildings
on all 4 sides One of the buildings is 3-storey and has a road on the
other side. Beyond the road is a row of houses with a playing field
behind and the bird I could hear was some/where out of sight behind that
building. There wasn't much bird activity in the garden because I was
out there, but the jackdaws in roughly the same direction were making a
racket - which is not unusual for jackdaws!
Jenny M Benson