Your PDF wwouldn't open for me, Graham, but this does from WIKI.
[ame="http://en.wikipedia.org/wiki/Giant_Hogweed"]Giant Hogweed - Wikipedia, the free encyclopedia@@AMEPARAM@@/wiki/File:Reuzenbereklauw.JPG" class="image"><img alt="" src="http://upload.wikimedia.org/wikipedia/commons/thumb/e/e0/Reuzenbereklauw.JPG/220px-Reuzenbereklauw.JPG"@@AMEPARAM@@commons/thumb/e/e0/Reuzenbereklauw.JPG/220px-Reuzenbereklauw.JPG[/ame]
It is an offence to cause it to grow, Huh?
Well the National Trust has allowed it to grow in Winkworth Arboretum, where once there was a lake and a fly fishing lake still exists there. Suddenly the stuff is everywhere along the valley and has now appeared in a local meadow from which the waters flow South to the Arun. I think it will start spreading both North and South from Godalming and it's darn near unstoppable.
One patch on the roadside in Hascombe has been dug up three times and holly planted. The holly couldn't take the road fumes and the Hogweed has re-appeared yet again this year. It actually seems to be spreading upstream !
Pretty as it is the local stream borders are rife with Himalayan Balsam, to the detriment of native plants.
Ruddy gardeners !!!!