W v Egdell 
A paranoid schizophrenic was detained in a secure hospital because he had shot 7 people, killing 5 and wounding 2. A psychiatrist was requested to evaluate his condition to prepare the transfer to a less secure facility / eventual release. The psychiatrist learned that the patient has interest in guns and bombs predated his disease. The psychiatrist sent the report to the hospital and the tribunal. The patient claimed the doctor had breached his duty of confidentiality.
The court held in favor of the restricted disclosure of vital information about the patient's dangerousness because of the grave concern for public safety.