"All adult patients (over 18) should presume their appointment/procedure has been cancelled unless they are contacted. Those who turn up will be turned away."
It's the computer system that has a virus not the doctor.
The patient knows what time their appointment's for and may already have arranged to take time off work.
The doctor knows what time they have a clinic.
In some cases the examination may be impeded by lack of access to the system but that's not necessarily the case for all examinations. Take written notes. They'll need to be put online later and if there were notes from a previous visit they'll need to be compared to those earlier notes and maybe an extra visit to take action that follows the comparison. But a hospital should not be totally dependent on functioning IT systems. It sounds like the decision of an administrator totally divorced from any perception of patients' circumstances. If they can manage without the system for younger patients why not for adults?