Well... No government, no politicians, no trial, no court, not sure about the will part. Yep, they need to define that better.
England clearly has the ability to try its leaders for war crimes -- it has courts and stuff -- so the ICC folks must have decided that it lacks political will.
If that's the case, then "lacks political will" is an almost meaningless and wide-open condition. After all, how often will a country have the political will to try itself for war crimes? The answer is never, which means that the ICC will always be charged to intervene, according to that condition. (this is assuming that the article stated the conditions accurately)
The thing that's exasperating is that Europe will accuse the US of imperialism or seeking hegemony or whatever, then it'll turn around and breathe into existence a global court with jurisdiction over all the world's citizens and constitional courts. That's pretty audacious, if you ask me.