Boundary fence between Standish Hospital and a neighbouring field.
I have counted at least 5 established knotweed sub-sites along the edges of this boundary alone, from where further, denser thickets can be seen within the grounds. From the position of some of the larger inner thickets, it's my personal guess that most of these are largely in situ in the same position as planted when the site was under private ownership throughout the 19th century. All the subsequent growth you see in the following images is from movement of plant material within the site(eg, attempts to thin, kill or clear). Needless to say, all such growth is firmly established.