Mike Jay quotes:

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.

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.

The Bedlam that greeted James Tilly Matthews, then, was not so much a baroque spectacle of depravity as an exhausted and run-down public institution, its building falling apart and its professional image tarnished.

To look back before 1800 is to enter another world, one where the number of institutions for the mad was a tiny fraction of today's and what we would now call mental disorders were often understood as religious ecstasies or diabolical possessions.

The Air Loom, for all its florid craziness, can be seen to have a function and a rationale: as a miraculous, if temporary, fix for a breaking mind, a coping strategy for a life that had become too brutally contradictory to sustain otherwise.

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

Haslam leaves us in no doubt what we are supposed to make of Matthews' mental world: this is gibberish and nothing more.

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

Up to this point, it was rare for the mad to be distinguished from the poor, the homeless, the indigent, beggars, vagabonds, petty criminals and others who were unable to fit into society or take care of themselves. It was rare, too, that they were locked up.

The Air Loom, if Matthews revealed its existence under questioning, would now be recognised immediately as a classic paranoid delusion. But in 1797 it was something that had never been encountered before, and would emerge as the baffling leitmotif of a case that was unprecedented in almost every imaginable way.

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 French army had crowned a campaign of extraordinary successes by defeating the Austrians at Jemappes and pressing on to occupy a large swathe of Belgium and threaten Holland. For Britain, this changed everything: a French republic that spread across the North Sea coast meant the entire coastline facing Britain would be in Republican hands."

We are now edging across the boundary - always a porous one - between self-justification and fantasy. Matthews' story is by no means a complete fantasy: we can recognise every event. But the frame of reference is somehow shrinking, and momentous world events being rewritten around the actions of a minor player.