If history is written by the victors, conspiracy theory is typically written by the losers, and there were few greater losers in the revolution than the French church and especially the Jesuits.

James Tilly Matthews was not a prophet. He was a gifted, perhaps fragile individual who suffered intensely, and for little if any reward.

Many had suspected that the political disasters of the past few years had a hidden cause. The bloodiness of the French mob rule was something unnatural, with a pitiless and inhuman progression that had never been seen before.

The Air Loom had been constructed by the Jacobins in Paris around the time of their coup d'etat in 1793. Just as they had corrupted the ideals of the Enlightenment to their despotic ends, so had they corrupted Enlightenment science. The secret of its power was pneumatic chemistry, the science of the invisible elements known as 'airs' or 'gases,' which had been developed by some of the great geniuses who had inspired the revolution.

We think of 1789 as the date of the French Revolution, and the storming of the Bastille as its defining event. Yet as late as halfway through 1792, most of the familiar images of the revolution had yet to occur. Louis XVI was still king, and the Assembly was negotiating a new constitutional arrangement for the monarchy, not so different from Britain's Glorious Revolution of 1688.

The French revolution, he concluded, had not produced any new principles of truths, merely a mass of examples of how things could go wrong.

At Bow Street Magistrates' Court the essential facts were established. The man's name was James Tilly Matthews. He was a pauper of the south London parish of Camberwell. He had a wife and a young family. He appeared to be of unsound mind.

Matthews' shout of treason in the House was no random outburst of lunacy, but the last act in an astonishing adventure: one that might indeed have changed the history of Europe. But by this point there was no-one left to confirm the truth of the story. Most of the witnesses were dead, and those who were alive were not interested in talking.

As a pauper, the obvious destination for James Tilly Matthews was the Bethlem Hospital, already long known in popular slang as Bedlam. The principal public asylum in London, it had accepted dangerous and insane paupers as 'objects of charity' for centuries, and was proud of the claim that it had never turned anyone away.