greater bird's foot trefoil

A bird's foot trefoil has established itself in my back garden lawn, as a result of an unaggresive mowing regime.

Yesterday I checked it, and it turns out to be the greater bird's foot trefoil (Lotus pedunculatus), distinguished from the common bird's foot trefoil (Lotus corniculatus) by possessing hollow stems. Of the other distinguishing features I don't really trust size, though this does seem to be bigger than the general run of the other, and the hairiness doesn't stand out. It is however a wet location (due to heavy clay soil, and lack of winter sunshire), which corresponds to the habitat of Lotus pedunculatus; Lotus corniculatus grows in dry locations. I'll have to keep my eye out for other bird's foot trefoils growing in wet localities.