A metre within the site: despite evidence of weedkiller application, knotweed here emerging from beneath extensive waste tip.
As images show, it makes light of being buried, strimmed, hacked, burnt: it emerges healthily from rusted metal sheet, concrete and rolls of carpet and the like.
A cogent, systematic, costed and monitored remedial action plan would be instrinsic to knotweed's control here. Such a plan necessitates several years of monitoring and intervention. It is incumbent on the owner of the site to notify affected parties and engage with the necessary moral and legal machinery. Under present UK law, such a landowner may be liable for damages and loss caused if knotweed escapes from its site..even for having knowledge and failing to act. I'd guess it would be helpful to local farmers, public, groups and interested parties to render such a plan immediate and transparent.