The King and Queen were immensely popular at the outset. But Marie Antoinette soon found herself vulnerable to the whims of the French public, and her popularity began to wane. There were continued rumours of her taking a series of lovers; though one courtier, the Prince de Ligne, wrote that she had "a charming quality of obtuseness which kept any lovers at a distance".

The satirical pamphlets, or libelles, while inventing freely on the subject of Marie Antoinette's lewd conduct, had more of a case when it came to her sense of fashion. Her mother, the Empress Maria Theresa of Austria, waxed indignant when she read about her coiffures, three feet high, bedecked in feathers and ribbons. "A young and pretty Queen, full of charms, has no need of these follies," she fulminated.

It could be argued that the Queen of France - which was the fashion centre of the world - had a duty to be modish. But by the end of 1776, Marie Antoinette, who had a dress allowance of 150,000 livres, had managed to incur liabilities of nearly 500,000 livres.

She was also spending large sums of money on gambling, and a small fortune on the Petit Trianon, a model village in the grounds of Versailles. More than a thousand white porcelain pots, decorated with the Queen's blue monogram, were designed to be filled with flowers so as to ornament the exterior of the model village's 12 cottages. (Despite the myth, she never actually dressed up as a shepherdess or a dairymaid, neither guarding sheep nor milking cows personally.) "All that fuss over a Swiss village!" exclaimed one court visitor.

Certainly Marie Antoinette had expensive tastes, but no more than others of her milieu - several members of the nobility spent far more on the rustic follies in their own grounds. And it would be quite wrong to give the impression of a thrifty King married to a free-spending Queen, to say nothing of the extravagant habits of the rest of the royal family.

Marie Antoinette's reputation was also damaged by the relentless demands made by her brother, the Holy Roman Emperor Joseph II. He urged her to take "the finest and greatest role that any woman ever played", using her as an important chess piece in his predatory foreign schemes. He demanded that Marie Antoinette exert her influence with the King.

Marie Antoinette's growing unpopularity with the French people was noted by Count Fersen - himself a rumoured lover of the Queen - who returned to France in 1785 after several years away. He noted how coldly Marie Antoinette was received when she entered Paris, as was customary for a queen following an accouchement (she had just given birth to her fourth child), reporting that not a single acclamation broke the perfect silence.

Marie Antoinette was the perfect scapegoat - being both female and foreign - for the political troubles of the King, troubles that had at their root the impossible financial situation of the Crown (the Treasury was on the verge of bankruptcy after a series of bad harvests). The blame was attached almost entirely to the Queen, who in the summer of 1787 was derisively called Madame Deficit.

In response, Marie Antoinette launched her own propaganda exercise, promoting herself as the fecund Mother of the Children of France, commissioning a portrait to promote this image from the artist Madame Vigee Lebrun. The portrait was intended to be shown at the Salon of the Royal Academy at the end of August. In fact it had to be withdrawn, as the Queen's unpopularity was so great that demonstrations were feared. The empty frame was left. Some wag pinned a note to it: "Behold the Deficit!"

On July 10, 1789, the great prison fortress, the Bastille, was stormed by a determined crowd who wanted the weapons and powder that they believed were stored there, in order to arm themselves against the state.

Several key members of court were advised to leave the country. At first, the Comtesse Yolande de Polignac, the Queen's favourite, refused to go, but the Queen was in agonies of fear every moment the Comtesse remained in France. In floods of tears, Marie Antoinette told her: "I am terrified of everything; in the name of our friendship go, now is the time for you to escape from the fury of my enemies. Don't be the victim of your attachment to me."

Why did the Queen - the most unpopular member of court - stay behind? The answer lies in Marie Antoinette's concept of duty. Frightened as she was by the grim spectre of her unpopularity, and apprehensive that there might be worse to follow, Marie Antoinette was nevertheless determined to preserve her position as the King's wife and the Dauphin's mother. So began an eerie summer at Versailles. In Paris, as throughout France, there were bread riots. The prospect of starvation made the women, in particular, increasingly aggressive on behalf of their families.

On Monday, October 5, the routine at Versailles still had a semblance of normality. The Queen was at the Petit Trianon. The King was out shooting. He had killed some 81 head of game when he received an urgent message that a march of market-women had set out from Paris for Versailles, intending to demand grain or flour from their sovereign - as well as his assent to constitutional change.

By six that evening there was an uneasy stand-off between the seething crowds in the courtyard of Versailles and the royal family. (It was at the point that, legend has it, the Queen exclaimed "Qu'ils mangent du brioche" - "Let them eat cake" - though if she uttered these words at all it would have been years earlier, during the Flour War of 1774.)

The original objective of the mob of securing food had been overtaken by the idea of transferring the King bodily to Paris, thus symbolically removing him from his Versailles power base. The royal bodyguards quickly became alarmed by the oaths they overheard - vows to cut off Marie Antoinette's head and worse. There were, for example, the proud declarations of the market-women that they were wearing their traditional working aprons in order to help themselves to her entrails, out of which they intended to make cockades.

That night, the Queen refused to share the apartments of the King, where she would have been safer, in order not to put him and her children in danger, and at two o'clock went to lie, sleepless, on her own bed.

The attack came at about four o'clock in the morning. The Queen fled her apartments for the King's, and the howling mob broke in. According to several accounts, they pierced the Queen's great bed with their pikes, either to make sure she was not hiding, or as a symbolic act of defiance. The royal family was rounded up and transported by the frenzied mob to Paris.

They were installed in the decaying Palace of the Tuileries in Paris. The financial allowance given by the National Assembly to the King for his living expenses - 25 million livres - was not ungenerous. In many ways Marie Antoinette's own domestic life was unchanged. But abuse was heaped upon her whenever she went walking outside the grounds, people deliberately splashing her with their carriages, calling out taunts and names.

The scabrous pamphlets attacking the Queen reached fever pitch. Drink, lesbianism, sexual voracity generally ("three quarters of the officers of the Gardes Franaises had penetrated the Queen") featured in works such as The Memoirs of Antonina, printed in London in two volumes. Owing to the demands of such numbers on her time, the Queen was described as preferring lovers in the style of a grenadier "who abridges preliminaries and hastens to the conclusion".

"Oh my God!" Marie Antoinette wrote to her brother Leopold in October 1790. "If we have committed faults, we have certainly expiated them." She felt misunderstood by the French, who were "a cruel, childish people".

In August 1792, after an attack on the Tuileries by revolutionaries, the royal family - in future to be known only as the Capets - were moved to the Temple, the palace of the exiled Comte d'Artois. Marie Antoinette had always had a horror of the medieval palace. "You see they will put us into the Tower," she wrote. "They will make a real prison for us." A wag affixed a placard to the Tuileries: "House to let."

Now the work of the Tribunals of the National Assembly began in earnest. The Princesse de Lamballe - one of the Queen's favourites - was brought before a tribunal but refused to denounce the King and Queen. Afterwards terrible stories were told of her fate: that she had been violated, alive or dead, that her breasts and genitalia had been hacked off or that, in another variant of savagery, her heart had been cooked and eaten.

Unquestionably, the Princesse's head was cut off and mounted on a pike. The crowd then decided to parade it to the Temple so that Marie Antoinette could bestow a last kiss on those sweet lips she had loved. When Lamballe's head on its pike appeared bobbing up and down outside the windows of the dining-room of the Tower, Marie Antoinette was frozen with horror. Her daughter, Maria Therese, later wrote that it was the only time she saw her mother's firmness abandon her. The Queen then fainted.

The sound of drums on December 11, 1792 announced the arrival of soldiers to take the King to be interrogated prior to his trial. He faced a denunciation for treason.

It was decreed that Louis XVI could, during the coming proceedings, either keep his children in his own quarters, or leave them with their mother and renounce all contact with them. Nobly, he commended them to his wife. "I have never doubted her maternal tenderness," he wrote in his will. He also begged Marie Antoinette to forgive him "all the ills she has suffered for my sake and for any grief that I may have caused her in the course of our marriage, as she may be certain that I hold nothing against her".

The guilt of Louis was easily established. In total, 691 members of the National Convention voted that he had conspired against the state; there were a few abstentions but no one voted against.

The family was allowed down to the King's apartments that evening. It was a piteous scene. The Queen huddled against the King, holding Louis Charles, their surviving son (Louis Joseph, the former Dauphin, had died of TB in 1789). The little boy clutched both his parents' hands tight, kissing them and crying. Maria Therese shrieked aloud.

It was the sound of drumming shortly before half past ten, followed by loud shouts of joy from the spectators, that told the listeners in the Tower that the King was dead. Marie Antoinette could not speak.

Two weeks later, the martyrdom of Marie Antoinette commenced. On the night of July 3, commissioners arrived at the Tower and brusquely informed the Queen that she was to be separated from her son. Louis Charles flung himself into his mother's arms, crying out. For the next hour she absolutely refused to release him. Threats to kill her left the Queen unmoved; only threats to kill Maria Therese produced some kind of reaction. Finally her resistance broke down. Marie Antoinette no longer had the strength to dress her son before he was led away - that was done by Maria Therese - and had to be content with wiping away his tears before being taken to the Conciergerie prison.

Her appearance in a crowded courtroom on October 14, 1793, caused an immediate sensation. The 37-year-old Queen looked ghastly. Here was a white-haired woman with sunken features and an extreme pallor. Her haggard appearance contrasted bizarrely with the mental image that most of the spectators had of her. If she was not the Austrian she-wolf, then she was the glittering Queen with her diamonds and her nodding plumes, last seen properly in the glory days of the Versailles court more than four years before.

Among the many charges brought against Marie Antoinette, arguably the most cruel was that she had sexually abused Louis Charles. The eight-year-old boy had been cajoled into making these accusations by his jailers, who had been feeding him a diet of wine and violence. When forced to answer them in court, Marie Antoinette's marble composure deserted her. "If I have not replied," she said in a tone quite changed from the politely indifferent one she had previously been using, "it is because Nature itself refuses to respond to such a charge laid against a mother."

At the very last, after 16 hours in the courtroom (and 15 hours the previous day), she was asked if she had anything further to say in her defence. "Yesterday I did not know who the witnesses were to be," answered Marie Antoinette. "I was ignorant of what they would say. Well, no one has articulated anything positive against me. I finish by observing that I was only the wife of Louis XVI and I had to conform to his wishes."

On Wednesday October 16, 1793, the head of Antoinette was cut off cleanly at 12.15 precisely, and exhibited to a joyous public. The body, together with its severed head, was taken unceremoniously to the graveyard off the rue d'Anjou, where Louis XVI had been interred nine and a half months previously, and where, more than 20 years before, the spectators who had been crushed in ecstatic celebrations at the couple's wedding had been buried.

Back at the Conciergerie, the effects of "the Widow Capet" were listed as follows: a few linen chemises and corsets in fine toile; two pairs of black stockings; a box of powder, a "big fine sponge", and a little box of pomade - the last remnants of a toilette that, in all its pomp, had once preoccupied the whole of Versailles.