IT looks like some variety of Tradescantia. I have loads in my garden with the funny blue flowers which look like ET.

Look like sunflower buds to me

I'd go sunflowers too.
I get these thanks to the squirrels and birds scattering seed about. they look like they are a multi headed version.

The leaves don't seem to match sunflower leaves - not any kind I've seen anyway. These look too narrow & longish - like tradescantia.

Ok, this was the first thought in my mind when a saw it, Cannabis?

It is most certainly not Cannabis.

the leaves aren't too bad a match for the sunflowers I have growing. Slightly toothed and clustered around the flower head. The Tradescantia I have, have parallel veins.
I agree not cannabis, though I have grown that in error thanks to the birds. embarrassing when we have a circle of friends that includes 3 police officers. none noticed it or if they did they didn't comment on it.

Please will you show us the flowers when they have opened?

Only thing I've grown that looked like that was the edible amaranthus Callaloo. It's a diverse group so may be a wild version?

I just posted a couple pictures of tradescantia from my garden (with the funny blue flowers I think look like ET). See if you think the leaves are a match.

lovely photos Paul but the leaves have parallel veins and the one posted by loosestrife has non-parallel veins.
these leaves also clasp the stem .

I have found a few more of these in the garden which I will leave alone to see the final outcome. The topping to that plant just reminded me of some similar looking dried plant material that I found in a ziplock bag at curbside.

I'm still not clear about how much stem was attached to those plants & whether it looked like sunflowers?
It's not hemp or cannabis! So you can calm down on that potential source of illicit income😄

This can't be cannabis which has palmate shaped leaves.

Evening Primrose?