Confidence: I'm as sure as I can be.
Notes: Not Vicia sylvatica, which has conspicuous tendrils at the ends of the leaves. Also if the colour rendering is correct, flowers are of the wrong colour. In fact, not a Vicia at all, since it has a terminal leaflet to the leaves rather than a tendril, a point, or nothing.
I think this is Sainfoin and probably subsp. decumbens, which crops up in "wild flower mixes" and seems to have more heavily marked, often paler, petals than the native subsp. collina.