It's an annual, growing to about 10-20 cm. It does not seem to flower, unless some of the pale green growths are petals and not leaves; but it does spread.
It is easily killed with a hoe, unless it's too close to another plant. I can't eradicate it as new plants keep appearing.
The location is England.
I have looked at lots of pictures of weeds, but found nothing like it.
