I moved into my current house last summer and at the time this plant was growing in the middle of a seating area. It was right in the middle so looked quite random. It was about 4ft tall then, not many side shoots and just generally looked odd. I assumed it was a weed/shouldn't have been there so cut it down to a few inches.
I didn't have time to get the root out so I placed these bigger stones around it so I didn't trip over it and added it to my list of things to do. However, now it's growing as in the photo, it's somehow forced its way through the stones.
Does anyone have any idea what it might be please? Thank you