Having Presence

What makes someone have a presence has always interested me. By presence I mean the ability to get (maybe even command) people's attention without going out of one's way to attract it.
As I write this I recognize that there is a superficial element to this and without doubt a tall, attractive individual of either sex is going to be able to turn-heads. But what I mean here is something deeper, a sense of an individuals aura and their power to influence a group.
The best example I have seen of this is at a high-school I taught at a long time ago. The principal, who was a nun, had a quiet calm about her which was most evident when she ran the school assembly. Getting the attention of over a thousand young and excitable students required the skills and poise of a seasoned lion-tamer (strange analogy but one that came to mind). Yet this lady would walk up to the microphone to signal the start of the assembly, and wait for the noise to dissipate as she got the students' attention. It did not take long, and if the response was not quick enough some students would take it upon themselves to shush the rowdier members of the student body. At worst, a few gestures and calming words from the principal would bring the assembly to order - all very orderly.
To understand the lady's presence one had to witness other assemblies being run by lesser individuals, where threats had to be made, individuals singled out and eventually, the speakers simply had to talk above the hub-bub.
How does one achieve that? Command the respect and attention of a mass of excitable school girls? It is of course not simply the individual, a carefully crafted but subtle ceremony helps achieve the desired order. However the individual is an integral part of that ceremony and creates the group dynamic and calming the individual students so that they can listen
It is about what is said; verbal cues. How it is said; the cadence of the voice, the stillness of the speaker asserting his or her authority, confidence and experience.
It may be a power play after all ..... but some individuals have the grace to make it appear natural.
Born leaders? Perhaps. Or possible great performers. Either way, when it works it is most impressive.