It is believed that London Stone originally served Roman London as a milliarium, or milestone, from which the distances of the Roman high roads were measured.
As the Romans held their boundaries in respect, the later reverence felt for the stone might have sprung from this source and increased by a natural growth.
Nevertheless, there are some who argue that the stone was a sacred memorial before the Romans built Londinium - that even then it had made itself secure on the site of their Forum.