13. When an operator acts in accordance with the instructions of a public authority, and as a result causes or threatens to cause environmental damage, and accordingly is obliged to take action under regulations 9 or 10, or if the enforcing authority takes action under regulation 11, then, unless the instruction related to an emission or incident caused by the operator’s own activities, the operator or the enforcing authority may recover the costs of actions under those Regulations from that public authority.