Seems to be a weighted system whereby the development company, who aren't liable for subsidence remediation (unless risk assesments/mitigation have been shodily done), gets the green light from the council, who also aren't liable. Liability for making it right is with central government (via the Mining Remediation Authority, under the Coal Mining Subsidence Act 1991) So the two parties actually deciding whether to build on a known coalfield, the company proposing it and the council approving it, both get to weigh housing targets and profit against a risk that, if it materialises, someone else entirely pays for - That collectively being us.