Hi David, the dreaded turned down edge. You also seem to have a slight hill at the centre as well but that is pretty easy to fix. What works for me is mirror on top, 1/4 strokes centre over centre, no sideways movement. I do this for about 10 minutes. Leave the mirror on the pitch for 15 minutes, test the mirror, and put the mirror back on the pitch for 1/2 hour to let the pitch catch up to the mirror. It's a slow process but the pressing of the lap is essential. If the hill in the centre gets bigger ,as it probably will, because by doing shorter strokes you are making the centre less deep do a couple of turns of 1/3 strokes but make sure that they are no longer than 1/3 strokes. I have removed turned down edges by doing this just proceed slowly, (patiently), and remember lots of pressing. This could take a while but it's worth it. Let me know how you go. Go to this link
http://cmabar.googlepages.com/home click on the mirror making link and see the paragraph obove polishing for a trick that I use. The website is a work in progress.
Regards Cristian