A 52-year-old man with type 2 diabetes undergoes elective knee arthroscopy under spinal anaesthesia. The anaesthetist administers 3 mL of 0.5% bupivacaine intrathecally without obtaining written informed consent, claiming the patient verbally agreed. Postoperatively, the patient develops cauda equina syndrome and files a complaint with the Medical Council. What is the most appropriate next step in addressing the medicolegal aspect of this case?