On a steep south-facing grassy calcareous slope in northern France
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Yes. Species Polygala - you can confidently add this as an id. However, I think unless you meet a real expert on flower shapes, it's safer to stick with genus without a careful view of the whole plant. Chalk Milkwort has a rosette of slightly larger leaves near its base (provided nothing's eaten them). Common Milkwort has the biggest leaves higher up the stem. Heath Milkwort, unlike the others, has some lower leaves opposite and is very unlikely to be growing on chalk. I think with this shade of blue the other UK species are ruled out. Not sure if there are more to find in France. People do claim that it is possible to distinguish Common from Chalk Milkwort by the the shape of the flowers, but I've struggled to see the difference.
Lat/Lng: 49.862, 1.7983
OS grid ref: TW730026