Coin with head of Alexander

Empire Builders (300BC - 1 AD)

Silver coin showing Alexander the Great (made between 305 and 281 BC). Minted in western Turkey

Welcome back to this second part of 'A History of the World in 100 Objects' here at the British Museum. I'm starting this week just over two thousand years ago, with the great empires of Europe and Asia - empires whose legacies are still strongly felt in the world today - the Roman Empire in the West, the Empire of Ashoka in India, and the Han Dynasty in China.

In this age of great rulers, I'll be looking at how power is constructed and projected. Military might is just the beginning - you might say it's the easy part. How does a ruler stamp his authority on the very minds of his subjects? As always, images are more effective than words, and the most effective of all images are those that we see so often that we hardly notice them. The ambitious ruler shapes the currency: the message is in the money.

"I'm standing in front of the very coin that shows the idealised Alexander, struck forty years or more after his death by his successor Lysimachus, in beautiful silver." (Robin Lane Fox)

"I think the nearest we've had in the modern world to the spread of Alexander's portrait in the Hellenised world . . . I suppose it's Napoleon, where busts of Napoleon were all over Europe. Then you have to come through to the dictators, I suppose - Hitler and Mussolini." (Andrew Marr)

I'm going to China soon, and I've just got back from my local bank, where I was changing sterling for Yuan. And what struck me most, as the red notes were being counted out, was that almost every one of them has on it the portrait of Chairman Mao. It's ironic isn't it, that this spectacularly successful capitalist economy carries on its currency the portrait of a dead Communist revolutionary? We all know why: Mao reminds the Chinese people of the heroic achievements of the Communist Party, which is still in power. He stands for the recovery of Chinese unity at home and prestige abroad, and every Chinese government wants to be seen as the inheritor of his authority. Of course this kind of appropriation of the past, this kind of exploitation of an image, is nothing new. In the world of high politics, it's been around for thousands of years, and what's happening today to Mao's image on the Chinese currency was happening over two thousand years ago to the image of another great ruler.

Today's object is one of the earliest coins that we know with the image of a leader on it - it's from around 2,300 years ago and it carries the head of the most glamorised military ruler of his age - and possibly of all time - Alexander the Great.

He's on a coin about an inch and a half (3.8 cm) in diameter, so slightly larger than a two penny piece. What I'm looking at is the profile of a young man - his straight nose and his strong jaw line show classical good looks and strength, and he's looking keenly into the distance - the tilt of the head commanding and suggestive of vigorous forward movement.

We've got no way of knowing whether this is an accurate likeness of Alexander but it must be him, because as well as human hair this man has ram's horns. It's the horn symbol, well-known throughout the ancient world, that leaves the viewer in no doubt that we're looking at an image of Alexander the Great. The horns are associated with the god Zeus-Amon - a hybrid of the two leading Greek and Egyptian gods, Zeus and Amon. So this small coin is making two big statements - it asserts Alexander's dominion over both Greeks and Egyptians, and it suggests that, in some sense, he is both man and god.

Alexander the man was the son of Philip II of Macedon, a small kingdom a few hundred miles north of Athens. Philip expected great things of his son and he employed the great philosopher Aristotle as Alexander's tutor. Alexander came to the throne in 336 BC at the age of 20, with an almost limitless sense of self-belief. His goal was to reach the "ends of the world and the Great Outer sea", and to do this he embarked on a series of wars, crushing rebellions by Athens and the other Greek cities, and then turning east to confront the long-standing enemy of the Greeks - Persia. Persia was at that point the greatest empire on earth, sprawling from Egypt across the Middle East and central Asia to India and almost to China. The young Alexander campaigned brilliantly for a total of ten years, until he had defeated the whole of the Persian Empire. What drove him on? We asked the leading expert on Alexander, Robin Lane Fox:

"Alexander was driven by the heroic ideals that befitted a Macedonian king, ruling over Macedonians, the ideals of personal glory, prowess. He was driven by a wish to reach the edge of the world, in his case first the eastern edge, denied by his men in India. He was driven by a wish to excel forever his father Philip, who was a man of significance, but pales almost to a shadow beside Alexander's global reputation."

Alexander's victories didn't just depend on his armies. They needed money - and lots of it. Luckily his father Philip had conquered the rich gold and silver mines of Thrace, the area that straddles the modern borders of Greece, Bulgaria and Turkey, and that financed the early campaigns. But this inheritance was later swelled by the enormous wealth he captured in Persia, and Alexander's imperial conquests were bankrolled by nearly five million kilos of Persian gold.

With irresistible force, huge wealth and enormous charisma, it's no wonder that Alexander became a legend, seeming to be more than mortal, literally superhuman. And for many, he was just that. In one of his early campaigns in Egypt, he visited the oracle of the god Amon, and there the oracle named him not just the rightful pharaoh of Egypt, but a god. He left the oracle with the title "son of Zeus Amon" - and that explains the characteristic ram's horns on images of him, like the one on our coin. He was received by many of the conquered peoples as though he were a living god, but it's not altogether clear whether he actually believed himself to be one. Robin Lane Fox:

"He certainly believed he was the son of Zeus in some sense . . . Zeus had entered into his begetting - a story possibly told to him, by that mother Olympias herself, though he is in earthly terms the son of the great king Philip. He is honoured as a god - spontaneously by some of the cities, by no means all, in his empire - and he is not displeased to receive honours equal to the gods. But he knows he's mortal."

Alexander conquered an empire of over two million square miles, and founded many cities in his own name, the most famous of course being today's Alexandria in Egypt. Although nearly every large museum in Europe has an image of Alexander in its collection, they're not consistent, and there's no way of knowing whether he actually looked like any of them. It was only after Alexander's death in 323 BC that an agreed, idealised, image, constructed for public consumption, came into being. And that's the image found on our coin, which, if I turn it over, actually reveals that this is not Alexander's coin at all - he's making a posthumous guest appearance in somebody else's political drama.

This side shows the goddess Athena Nikephoros, bringer of victory, carrying her spear and shield. She is the divine patroness of Greeks and a goddess of war. But it's not Alexander that she's favouring, because the Greek letters beside her tell us that this is the coin of King Lysimachus. Lysimachus had been one of Alexander's generals and companions. He ruled Thrace from Alexander's death until his own death in 281 BC. So why didn't Lysimachus mint a coin that showed himself? The answer is quite simple: he's trying in this coin to appropriate the glory and the authority of his predecessor. This is image manipulation - almost identity theft - on a heroic scale. Robin Lane Fox again.

"It's a superb example of Greek Hellenistic coin portraiture, based on the prototypes of the great gems commissioned by Alexander, who controlled the artists who could make his image. It reminds us it's a world of monarchy, it's a world of association with Alexander, it's a world of exquisite art and it's a world of publicity forming a climate of opinion - all too familiar!"

Alexander died in his early thirties, and his empire quickly disintegrated into a confusion of shifting territories under competing warlords - Lysimachus was just one of these. All of the war lords claimed that they were the true heirs of Alexander, and many of them minted coins with his image on them to prove it. This was a struggle fought out not just on the battlefield but on the coinage. It's a textbook early example of a timeless political ploy: harnessing the authority and the glamour of a great leader of the past to boost yourself in the present. Dead reputations are usually more stable and more manageable than living ones. Since the Second World War, for example, Churchill and de Gaulle have been claimed by British and French political leaders of all hues when it suited the day's agenda. But in democratic societies, this is a high-risk strategy, as Andrew Marr, the political commentator, points out:

"The more democratic a culture is, the harder it is to appropriate a previous leader . . . I mean it's very interesting at the moment to see the revival of Stalin for instance in Putin's Russia as an admired figure, having been knocked down as a bloodthirsty tyrant before. So the possibility of taking a figure from the past is always open, but as I say the more conversational, the more confrontational, more democratic, the more argumentative a political culture is, the harder it is.

"You can see this in the case of Churchill, because there are still lots and lots of people who know a great deal about what Churchill thought and said. Any mainstream party which tried to say 'we are the party of Churchill' would get into trouble, because Churchill changed his mind so much that he can be quoted against you as often as he can be quoted in favour of you."

Dead rulers are still very present, and they're still on the currency. A thoughtful alien handling the banknotes of China and the United States today might well assume that one was ruled by Mao and the other by George Washington. And in a sense, that's exactly what the Chinese and American leaders want us all to think. Political giants like these lend an aura of stability, legitimacy, and above all of unquestionable authority, to modern regimes struggling with huge problems. Lysimachus's gambit still sets the pace for the world's superpowers.

And it worked for Lysimachus himself, up to a point. He's a mere historical footnote in comparison to Alexander - he didn't get an empire. But he did get, and he hung on to, a kingdom. Twenty years after Alexander's death, it was clear that his empire would never be reconstituted, and for the next three hundred years the Middle East would be ruled by many cultured but competitive Greek-speaking kings and dynasties. In a later programme this week I'll be looking at probably the most famous monument of any of these Greek-speaking states, the Rosetta Stone, but in the next programme I'll be in India, where the great emperor Ashoka linked himself to a different kind of authority to strengthen his political position. Not the authority of a great warrior, but of one of the greatest of all religious teachers . . . the Buddha.