Working alone is not in itself against the law and it will often be safe to do so. However, the law requires employers and others to think about and deal with any health and safety risks before people should be allowed to work alone.
An employer must ensure that all lone workers are physically fit before commencing work. A Lone Worker medical will assess just that and will advise on any particular emergency equipment and procedures that may be required.
As a minimum the Lone Worker Medical will include a questionnaire and a consultation with a nurse or a doctor.