version 1.

version 2.

Burning the sky and dodging the horses to add some drama
version 3.

Slightly subtler effect, as suggested by
The Brentford Taylor. I made the sky into a new layer and adjusted the levels and curves, then blended it into the original using the 'multiply' blending option. Rather than use the dodge tool on the horses I brightened the foreground.
~ Port Meadow, Oxford