Solved plant id please

Wondering if anyone knows what this is? It looks weedy, and similar to willowherb, but I don't think it is (I've checked the weed photos and its leaves don't have the serrated edges). Google is struggling with it as well. But I'd like confirm what it is before pulling it up.
Thanks

 

Pic turned to see if that helps.

Agree it is not Chamaenerion angustifolium...common name Rosebay willow herb it has alternate leaves.
Mystery plant leaves appear to be opposite to each other.

 

Looks like it's phlox, probably meadow phlox. So I think I'll leave it.

 

Quote....
"Phlox maculata, commonly called meadow phlox, as well as wild sweet William and marsh phlox, is a species of flowering plant in the family Polemoniaceae, native the eastern United States and introduced to eastern Canada. It is a perennial. Wikipedia"

I wonder where this idea came from?
Hmm....do you live in USA?
I have never seen Meadow Phlox growing in UK.
This site shows very different leaves.

Phlox maculata (spotted phlox, wild sweet-William): Go Botany

 

I'm in the south of the UK. I was looking at the info here. Agree that some of the photos don't look quite right, but some of them do. I'm going to have to let it flower now, just to see what it is.

 

In case anyone's curious, it did indeed turn out to be a type of Phlox (I'd be interested to know which). Glad I didn't dig it up!

 

I'm sure it's Phlox paniculata