The article on the Olympic Delivery Authority's Japanese Knotweed problem (NCE 8 February) is a familiar one to me as I purchased a house in 1989 with the garden full of the stuff.
It certainly was not on the scale reported, but I did make some discoveries that may be of use.
The weed propagates through its root structure and the smallest amount left in the ground can restart the infestation. Spraying can work, but it is not as easy as what it says on the packet. The roots, some thicker than a man's arm, can survive numerous sprayings.
It is also dangerous. The liquid in the stems can bring up huge red marks on the skin.
The article appears to favour dig and dump but I have not found any advice that indicates that the roots will die below 5m.
One solution is to cook the roots. I placed a number of very hot bonfires over the area of the main infestation. It is important that the soil is heated deeper than the lowest root.
Most of the weed has now gone and I only get one or two shoots each year from the small bits I missed.
Julian Hartless (M), principal project manager, julian. firstname.lastname@example.org. uk