Clover or vetch or ?? in the Somme

Clover or vetch or ?? in the Somme

Observation - Clover or vetch or ?? in the Somme - UK and Ireland. Description: Large patch in a field, up to waste high, inflorescence like purple milk vetch ? but trefoil leaves like a clover?? Very popular with butterflies

Large patch in a field, up to waste high, inflorescence like purple milk vetch ? but trefoil leaves like a clover?? Very popular with butterflies