I can't comment on every bank but having worked for a couple in the past, on occassions where my staff visited one of these doctors the normal practise would be for the doctor to prepare a report which was usually sent to the HR department. As line manager I never got to see the report, albeit HR may give me a verbal synopsis on what was on there. most of the time it simply confirmed what was on the staff members sick cert.
In addition, if this was a long term sickness case and the employee was being moved off the payroll(assuming employer pay sick pay for a period) and onto long term insurance payments, insurers would also require such a report
An employer is not expected to hold open a position indefinately if a person is physically incapable of doing the job.