When I loosely call this Solidago canadensis, I don't really mean anything very definite except that it definitely isn't S. gigantea, because the stems are pubescent all the way down. The N. American species of Solidago (Goldenrod) are difficult, and garden material could be any kind of hybrid or varietal stuff. What stands out about this particular one, a gift from Ebs, is how late-flowering it is. These photos were taken on 16th October, when it was finally at its zenith.
Most other S. canadensis (using the name in its loose sense) is at peak in August or early September. It is now a familiar part of the British landscape, especially in the south, both in gardens and out of them, on the edges of fields, railway embankments, road verges etc.