Parabuteo unicinctus, did you say?

Last autumn, I was with David Hopkins in his yard watching a Harris's Hawk mobbing a Honey Buzzard. The latter is a summer visitor and despite its name, not really a buzzard. The former is an American raptor, much used in falconry, and despite its name more of a buzzard than a hawk The one we watched was clearly a falconer's bird, identifiable by the jesses and bells hanging from its legs.
Today, while scanning finch flocks on the fen in the hope of finding more Bramblings, I spotted a large bird of prey perched on a piece of farm machinery. It turned out to be a Harris's Hawk, presumably the same one that I had seen at David's last year.
The purists in the birding fraternity will tell you that you cannot "tick" such a bird because it is not a genuine wild bird. Well, sod 'em, I say. It's a gorgeous bird, with mahogany-coloured wings and "trousers", a heavy pale beak, white undertail coverts and a long dark tail with a broad white terminal band. Look at it and tell me it isn't worth drooling over!