Maya relief of royal blood-letting (made early eighth century AD). Stone; from Mexico

It's tough at the top - at least, that's what those at the top like us to think - the long hours, the public exposure, the responsibility. In return though, most of us would argue, they get the status and the pay - and most people it seems are willing to settle for that particular trade-off.

But, we'd all think twice, I suspect, about envying anyone, however privileged, whose regular duty was to go through an ordeal that sounds like this cry of pain . . . in this case that of a man in the Philippines, seeking and enduring excruciating physical pain, in order to achieve a transformed spiritual state. These days most of us take quite a lot of trouble to avoid pain. And wilful "self-harm" suggests to most people an unstable psychological condition. Sado-masochism gets, on the whole, a bad press, but around the world there are, as there always have been, believers who see self-inflicted pain as a route to transcendental experience. To the average 21st-century citizen, and certainly to me, this willed suffering has about it something deeply shocking. And so I find it hard even to look at the image that I'm going to be discussing in this programme.

"What I find startling about this horrific image is how visible the woman's pain is." (Susie Orbach)

"You can tell from her clothing, her jewellery and her elaborate head ornament that this is a woman of great status and wealth." (Virginia Field)

All the objects in the programmes this week are from the great royal courts of the world, around 800 AD. They're not objects that were made for public view - they're intimate, private expressions of great public power, objects created so that the rulers of the world could state and re-state the full extent of their authority to themselves, to their courtiers and to their gods. And, it must be said, the very real obligations that they saw as going with that authority.

I'm looking at a limestone relief carving, about the size of a small coffee table. It's rectangular, and it shows two human figures. A man,is standing holding a blazing torch over the kneeling figure of a woman, and both are elaborately costumed, with wonderful extravagant headdresses.

So far, so innocuous - but when I look more closely at the woman, the scene becomes horribly disconcerting. Because I can see that she is pulling a rope 'through' her tongue - and the rope contains large thorns, which are piercing and lacerating her.

My squeamish European eye keeps focusing on this stupefying act, but for the Maya, what would have been important was the whole scene. For this is the king and his wife, together in a devotional partnership, jointly performing a ceremony that is of fundamental significance for their position and for their power. It was commissioned by the king to go into the queen's private building. And it was certainly intended to be seen by only a very select few.

The great Maya civilisation collapsed not long after this stone slab was carved, and their great cities, left deserted, bewildered the first Spanish visitors when they arrived in the sixteenth century. For hundreds of years afterwards, explorers travelling in southern Mexico and Guatemala came across huge abandoned cities hidden in dense jungle. One of the first modern visitors, the American John Lloyd Stephens, tried to describe his wonderment in 1839:

"Of the moral effect of the monuments themselves, standing as they do in the depths of the tropical forest, silent and solemn, different from the works of any other people, their uses and purposes and whole history so entirely unknown, with hieroglyphs explaining all but perfectly unintelligible, I shall not pretend to convey any idea."

Thanks to the relatively recent decipherment of Maya script, we can now read the images and the writing on their monuments as the names and histories of actual rulers. In the course of the twentieth century, the Maya ceased to be a mythologized lost race and became a historical people.

Maya territory covered modern Honduras, Guatemala, Belize and southern Mexico. The first Maya cities have their beginnings around 500 BC - so just a little before the Parthenon was being built in Athens - and the Maya civilisation continued for well over a thousand years. The greatest Maya cities had tens of thousands of inhabitants, and at their centre were pyramids, public monuments and palaces.

Our stone sculpture of the queen lacerating her tongue comes from the city of Yaxchilan. Between 600 and 800 AD, so late in the classic Maya age, Yaxchilan became a large and important city, the major power in the region. It owed its new eminence to the king shown on the stone lintel, Shield Jaguar. At the age of 75, he commissioned a building programme to celebrate the successes of what would eventually be his 60-year reign. The lintel sculpture comes from a temple that seems to have been dedicated to his wife, Lady K'abal Xook.

On the carving, King Shield Jaguar and his wife are both magnificently dressed, with spectacular headdresses, probably made of jade and shell mosaic, and decorated with the shimmering green feathers of the quetzal bird. On top of the King's headdress you can see the shrunken head of a past sacrificial victim. On his breast he wears an ornament in the shape of the sun god, his sandals are of spotted jaguar pelt, and at his knees there are bands of jade. His wife, meanwhile, has spectacularly elaborate necklace and bracelets.

This image is one of three found in the temple, each one positioned above an entrance. Together they make it clear that the act of pulling thorns through the tongue was not just to make the Queen's blood flow as an offering, but was deliberately intended to create intense pain - pain which, after due ritual preparation, would send her into a visionary trance. For the Queen to inflict such suffering on herself was a great act of piety - it was her pain that summoned and propitiated the kingdom's gods, and that ultimately made possible the king's success. Here's psychotherapist and writer on women's psychology, Susie Orbach:

"If you can create a feeling of pain in the body and you survive it, you can move into either a state of, not quite ecstasy, but out-of-the-ordinariness, a sense that you can transcend, you can do something rather special.

"What I find interesting about this image, which is quite startlingly horrific, is how visible the woman's pain is. I think that, in the present day, we've come to hide our pain. We have the jokes about our capacity for pain, but we don't really show it.

"What we see there is something that women can understand and can reflect, although it's very exaggerated, the kind of relation to self and to a husband that a woman often makes - or to her children. And it's not that men are extracting them. It's that women experience their sense of self by doing these things, by enacting them. They give them a sense of their own identity. And I'm sure that was true for her."

The next lintel in the series shows us the consequence of the Queen's self-mortification. The ritual blood-letting, and the pain, have combined to transform Lady K'abal Xook's consciousness, and enable her to see, rising from the offering bowl that holds her blood, a vision of a sacred serpent. From the mouth of the snake a warrior brandishing a spear appears - the founding ancestor of the Yaxchilan royal dynasty, establishing the King's connection with his ancestors, and therefore his right to rule.

For the Maya, blood-letting was an ancient tradition, and it marked all the major points of Maya life - especially the path to royal and sacred power. In the sixteenth century, 800 years after this lintel was carved, and long after the Maya civilisation had collapsed, the Spanish encountered similar blood-letting rites that still survived, as the first Catholic bishop of Yucatan reported:

"They offered sacrifices of their own blood, sometimes cutting themselves around in pieces, and they left them in this way as a sign. Sometimes they scarify certain parts of their bodies, at others they pierce their tongues in a slanting direction from side to side, and pass bits of straw through the holes with horrible suffering. Others slit the superfluous part of the virile member, leaving it as they did their ears."

The unusual thing about our sculpture is that it shows a woman playing the principal role in the ritual. Here's Virginia Fields, expert on Maya iconography and art:

"This particular lintel at the British Museum is just an extraordinary example of the kinds of rights and ceremonies that a queen would engage in, they are extremely unusual. We don't have a series like this from another Maya city.

"We know that the royal women were part of lineages in every city. Lady K'abal Xook actually is from a local lineage in Yaxchilan, but by taking her as a wife, they may have been joining two powerful lineages. And then bringing in another wife from a foreign city extended the alliances that he had been creating with different powerful cities around the realm."

K'abal Xook's husband, Shield Jaguar, had an immensely long reign for the age, but within a few decades of their deaths, all the great cities of the Maya were in chaos. On the later Maya monuments, warfare is the dominant image, and the last monuments we know are around 900 AD. An ancient political system that had lasted for more than a thousand years had disintegrated, and a landscape where millions had lived became desolate. Why, remains one of the great historical mysteries.

Environmental factors are a popular explanation. There is some evidence of a prolonged drought, and given the density of the population, the decline in resources a drought would cause could well have been catastrophic. But, in all events, the Maya people of course, did not vanish. Mayan settlements continued in a number of areas and a functioning Mayan society lasted right up to the Spanish Conquest.

Today there are about six million Mayans, and their sense of their heritage is strong. You have just heard the sound of a Maya uprising in 1994, when the Zapatista Army of National Liberation, as they call themselves, declared war on the Mexican State. Their independence movement profoundly shook modern Mexico. "We are in the new 'Time of the Mayas' ", a local play proclaimed, as statues of the Spanish conquistadors were toppled and beaten into rubble. Today, the Maya use their past to renegotiate their identity, and seek to restore their monuments and language to centre-stage in public life. New roads now open up access to the formerly "lost" cities. Yaxchilan, where our sculpture came from, used to be accessible only by light plane or a river trip across hundreds of miles, but since the 1990s it's just an hour's boat ride, and it's a big draw for tourists.

The disturbing image on our sculpture shows a powerful woman using self-mutilation to induce a vision of divinely ordained authority. In the next programme, we're going to be looking at an altogether more appealing aspect of privilege. We're moving from the politics of pain in Mexico to the politics of pleasure in the Middle East... to the world of the Arabian Nights.