Birds foot trefoil, Lotus pedunculatus

Found on a range of damp grassland habitats including wet meadows, rush pastures, marshes, ponds, lakes and rivers with a slight preference towards acidic soils. Greater birdsfoot trefoil is the only British legume found in wetlands. It spreads by stolons and to a lesser extent by seed. 

It is not edible for us.

Being a trefoil it should also fix nitrogen from the air in its roots, thus enriching the soil.