My understanding is that, because they can plausibly deny being complicit in the illegal dumping, the landowner is currently able to refuse to pay for the remediation of the problem.

So why not attack that aspect of it? There could be some sort of strict liability offence, so that they're responsible for the costs of the cleanup without the need to prove their direct involvement.

That way the onus would be on the landowner to look after their land (using AI drones if they wish). Why should the taxpayer to be on the hook for it?

Andy Burnham promises drive to tackle toxic waste, raise fines and use AI-powered drones to detect illegal activity