Whilst immediately identifiable as a member of the pea family there is some thing very different about the yellow vetchling (Lathyrus aphaca) compared to other peas. The visual difference is, technically quite complicated!
I have to depend on my book here for an explanation. Whilst the yellow flower retains the characteristic appearance of a pea the leaves have become tendrils for supporting the plant and the stipules (the branches that lead to the leaves) have become broad, triangular pseudo-leaves. What appear to be leaves do not resemble those of a pea flower leaf at all; they are harder and seem waxy and the triangular shape is not in keeping with its cousins. Whist unusual features this does make the plant easily recognisable. Yellow vetchling flowers from June until August and is found in dry grassy places on limestone or chalk; in my experience this seems to usually be by the sea.
Although a pea the peas from the pod are best left alone. Although safe to eat in small quantities when young when they turn brown they become hazardous and can affect the nervous system if eaten in large quantities.