Evening sky landscape

A mono landscape, after the Open Skies book/collection by Don McCullin, on the Wolds between Wold Newton and Hunmanby, East and North Yorkshire.
I had to wait until the evening for the light to become interesting again, having missed the early morning fine weather.
This was shot about an hour before sunset.
Although I shot in colour too(which can be seen on my flickr page) I thought the mono image was far more striking.
I used a grad grey filter over the sky, but other than levels and sharpening in Photoshop, this is close to the photo straight from my GF1.