Paul - I think the reason no-one has responded to your post is because the link isn’t opening the photo - if you click on it you are taken to a “log in” page and told you are not authorised to view the content without signing in to flickr, so rather difficult if you don’t have a flickr account.

Whilst at Westhay Moor (North Hide) this morning where I saw the 3 Garganey I was trying to get a decent photo of a very distant Marsh Harrier when all of a sudden the Marsh Harrier was chased off by a smaller raptor. I only got 1 in focus shot of the back of it. Can anyone identify it please. The underside/breast of it which I saw clearly was white. Thank You

https://www.flickr.com/photos/paulcousins/47558490541/in/datetaken/