A person can demonstrate competence to perform electrical work if he or she has successfully completed an assessed training course that has included the type of work being considered, run by an accredited training organisation, and has been able to demonstrate an ability to understand electrical theory and put this into practice.
A successfully completed electrical apprenticeship, with some post apprenticeship experience is a good way of demonstrating competence for general electrical work. More specialised work such as maintenance of high voltage switchgear or control system modification is almost certainly likely to require additional training and experience.
[Source: HSE]