Another new to me - ID very tentative again. Another pic added
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... Geranium molle and Geranium pyreniacum when one has an idea of the scale.
...approx 1-2cm, hope this helps. Plant was 10cm high probably.
... the petals of G. molle are 4-6 mm long, and those of G. pyrenaicum are 7-10 mm long. If the flower size was towards the bottom end of your range it remains ambiguous and you need to consider other characters.
The character Stace gives is that G. pyrenaicum has smooth, hairy mericarps, and G. molle has ridged, glabrous mericarps (excluding the beaks), but in the absence of fruits you can't use that.
...bigger than 6mm - so 10mm minimum - would this not be G.pyrenaicum?
... were petal lengths, not flower diameters. The latter is what I thought you were referring to.
Flower diameters would be approximately double (on the one hand you have to add something for the gynoecium and androecium; on the other hand if the corolla isn't flat that reduces the diameter) the petal lengths, so the boundary would be somewhere around 12-14mm. I'd guess nearer 12mm than 14mm.
I do think that it's G. pyrenaicum, but I can't prove it. (Perhaps if I was to look up Flora Iberica I could find some additional discriminating traits.)
Lat/Lng: 51.3819, 1.3263
OS grid ref: TR315700