Is this a Harris' Hawk?

First post, all very exciting! I have noticed this bird several times over the last couple of years ago but couldn't get an ID. Then it came and sat in our garden for half an hour!

(The quality suffered when I converted the video for YouTube, but it's okay.)  My wife cleverly researched it and found several references to this Harris' Hawk, which noted that it's a foreign species most likely to have escaped from a falconry. The searches indicated that it's not numerous here: if it is a Harris' Hawk, are they properly rare?

Cheers,

Chris