Can anyone please identify for me?

Have a look at Black-winged Kite. I'm not saying it definitely is but the something about the face is very similar. Also check local face book to see if anyone has lost a Bird of Prey

Thank you so much for your reply. You may be right about the possibility of it being an escapee, if so, I also hope very much that it finds its way home safely.
I will certainly take a look at both Black-winged Kite and Gyr falcon. Whatever it is I feel very lucky to have seen it and only regret not having a better camera at the time.
Thanks again
John

Thank you Cris. Having taken a look online at Gyr falcons, I think both you and Germain have come up with the answer to my question, and what a wonderful answer it is. I must confess that I had never even heard of a Gyr falcon until today but I am so glad that you have both introduced me to such an incredible bird.
Thank you for your help
John