Regulation 11 Excavations
Every conductor below ground shall be placed at such depth as to avoid, so far as is reasonably practicable, any damage or danger by reason of such uses of the land which can reasonably be expected when the conductor is placed below ground.
In addition to satisfying the requirements of paragraph (1), a conductor below ground used in a supplier’s high voltage system but not connected with earth shall be laid in such manner (whether in pipes or ducts or so overlaid at such a distance above the conductor by protective tiles or warning tape or Some other protective or warning device or otherwise) as to ensure, so far as is reasonably practicable, that any person excavating the ground above the conductor will receive a warning of its presence.