This is such a tiny, inconspicuous flower that I am sure I have overlooked many times before. Being so small it also not easy to photograph hence the blurred picture! It occurs on dry sandy ground where the grass is sparse; this means usually paths or walls with some degree of soil on them. It is common where it occurs but has pretty specific habitat requirements which make it local over all!
You might have difficulty in seeing the petals in my photograph. That is because it has no petals, only green sepals.