Looks legally complicated in Britain for both patients and doctors according to this. Yet if the patient
isn't operating a motor vehicle as ordered, I'd think "no harm, no foul". Thus no need to formally notify the DVLA. But does it operate as such accordingly given the circumstances of the OP? I'm not sure.
"
Doctors will be obliged under new guidelines to report patients who continue to drive even though they are not medically fit to do so."
"As it stands doctors do not need a patient’s consent to inform the DVLA, which is legally responsible for deciding whether a person is medically fit to drive, when a patient has continued driving in such instances."
Doctors ordered to report patients unfit to drive to DVLA