Field Pansy. Viola arvensis

The delicate Field pansy is a wild relative of our garden pansy and can be found in fields and on waste ground and roadside verges - anywhere the ground has been disturbed. Its long-stalked, pale yellow flowers can be found winding their way through the grasses from April to October.
Field pansies are annuals, so they live for one growing season, flowering, seeding and dying off. Only the dormant seeds survive, ready for the next season.

The flowers are cream or pale yellow with cream upper petals and more rarely blue or violet. Each flower is about 10-15mm in size. You have to keep your eyes peeled to see them.