Interesting and helpful ideas, thanks. I should probably have said at the outset that both partial and 100% cropping are options I don’t want to consider!

So actually the first few suggestions are what I needed to hear.
The fact that several of you suggested cropping illustrates the problem: that unless I can emphasise it by printing you will miss the point. This was taken at the highest point in Brittany (France), a site used by the occupying German army in WW2 as a radio station. It’s a wide, desolate landscape, much cut about by man - not at all the kind of thing I had expected to see in Brittany.
These two guys could have been war historians or pilgrims or lepidopterists for all I know, but they had chosen to turn their backs on the little chapel, the disconcerting gun emplacements and the other tourists, and instead to sit apart looking out over this barely-covered rockscape and overcast sky.
If the point is lost, this photo is for the bin. But I still need to learn to deal with those overly-uniform tones, because this is a problem I face too often. This will do as an learning-piece. I will try split-grade along the lines suggested and see what I can achieve.