Which Bird of Prey does this?

I was walking the dog in Hertfordshire.
As we got near to town where I live I heard the frantic squawking of a bird of some sort. I looked up and saw a smaller bird being chased in a circular motion by a larger bird.  As I walked back the high pitched squawking continued as the bird flew higher and higher, till I could barely see them…….further and further away from the starting point. I then discerned another large bird seemingly joining in. As the smaller bird got more tired they tried to attack it…..several times. Eventually the squawking stopped.
We have a lot of Red kites, Buzzards and other birds of prey here. I’ve never seen this behaviour before, though I have seen crows chasing Kites away from their nesting areas.