Which Birdsfoot trefoil?

Which Birdsfoot trefoil?

Observation - Which Birdsfoot trefoil? - UK and Ireland. Description: This trefoil fits Common Birdsfoot trefoil for habitat - a chalk grassland slope - rather than Greater which prefers damp, acidic habitats; the low number of flowers per head also suggest Common; the size could fit either as it was around 30cm high (tall

This trefoil fits Common Birdsfoot trefoil for habitat - a chalk grassland slope - rather than Greater which prefers damp, acidic habitats; the low number of flowers per head also suggest Common; the size could fit either as it was around 30cm high (taller than Common usually is, shorter than greater usually is), but some posts suggest that if the sepals are recurved as I think these are, that makes it Greater (Lotus pedunculatus), so I'm wary of saying it's P. corniculatus... which was my initial ID. Any input/ species update welcomed...