Just this year I've got this growing all over the place wherever I haven't cultivated and would like to know what it is!
It looks like a member of the goosefoot family, My guess would be Good King Henry, Chenopodium bonus-henricus.
And if it is Good King Henry, you can eat it
I think I'd vote for fat hen. That's edible too, apparently
Thanks for that. Not sure I'll eat it though...
It looks as if it's mainly a problem in crop fields so I'm hoping it prefers recently dug ground. The places where it's growing were all part of a major landscaping project earlier in the year. A little bit worried that googling it suggests that a single plant can produce 20,000 seeds and that these remain viable for 30-40 years!
I can vouch for the seed viability information. I get this growing in my veg beds every year but always hoe or pull them up well before they set seed and have been doing so for about 30 years. Only 10 more years to go then and I'll be free of this blasted stuff..