I love how the light horse in the center of the frame is the only thing I focused on. I didn't even notice the rump in the lower right corner of the frame.
The way the light has struck the horse's mane is magical.
Thanks for comments. There is a humorous aspect to this picture - I had not encountered a herd of Dartmoor ponies before, so was stalking them and observing for some time (during which the fortuitous lighting effect occurred). I was congratulating myself on being stealthy enough not to disturb them. Eventually I moved closer, and then closer still, until I finally realised that the ponies were so used to human beings that you could walk right through the herd and they would not take any notice!
The horse in the center is doing something very typical of Dartmoor ponies - standing behind a rock so that its nose is out of the wind!