I think this is Slender St Johns Wort. Not that sure, however. Is it possible to tell from the photos?
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It fits with the description given in David Sutton: "Field Guide to the Wild Flowers of Britain & N. Europe (Kingfisher, London, 1988), who says "Slender St John's-wort has blunt sepals and mostly heart-shaped leaf-bases".
It doesn't, however, quite agree with my 1952 edition of CTW. This lists 14 species of Hypericum. Under H. pulchrum, it says "petals red-tinged, with a row of black glands near margin", none of which I can see in the photos.
Neither does it look much like the illustration in McClintock,D. & Fitter,R,S.R.: "tThe Pocket Guide to Wild Flowers" (BCA ex Collins), who call H. pulchrum the Elegant St. John's Wort.
I can't see what else it could be, however.
Lat/Lng: 54.174009, -4.497142
OS grid ref: SC371782
Grass covered rocky hillock. Heavily covered with oak tress. The plant sheltered from direct sunlight by these oak trees. Ground quite damp.