All work activity, including...... work near an Overhead Line system, shall be carried out in such a manner as not to give rise, so far as is reasonably practicable, to danger. No person shall be engaged in any work activity on or so near any live conductor (other than one suitably covered with insulating material so as to prevent danger) that danger may arise unless (a) it is unreasonable in all the circumstances for it to be dead and (b) it is reasonable in all the circumstances for him to be at work on or near it while it is live and (c) suitable precautions (including where necessary the provision of suitable protective equipment) are taken to prevent injury.