The post processing of this image is wonderful and there is no doubt that this entry meets the challenge. The subtle desaturation reflects upon your vast experience here at DPC.
Where this challenge entry misses the mark for me is two fold. First, almost all of the people have their back to the camera. There is no eye contact to help hold the viewers attention. Second, there is no story here. Obviously this is some sort of event but being from the other side of the pond, I have no clue as to what is going on or why these people are gathered together.
Feel free to PM me if you have any questions regarding this critique.
I think I like this because it's selective desaturation without immediately looking like selective desaturation. The clothing doesn't look "wrong" being only black, white and gray. It's not until you notice the gray grass that you realize something is different. And the red cross really draws your eyes in so that the gray grass isn't that big of a deal.