Prof Ged Martin follows an unstable young Frenchman from Romford to the gallows

Shortly after midnight on September 2, 1666, fire broke out in a bakery near London Bridge.

Fanned by an east wind, the Great Fire of London raged for five days, destroying St Paul's cathedral, 87 churches, most of the City's public buildings and 13,000 homes.

Refugees fled to nearby towns like Romford with cartloads of possessions snatched from the flames.

England was fighting the Dutch. The war was going well: in 1665, their American colony, New Amsterdam, had been captured and renamed New York.

But the French king Louis XIV had just allied with the Dutch. The Great Fire looked like a double whammy.

In 1605, Guy Fawkes had led a Catholic conspiracy to blow up James I and Parliament. Some Catholics in Ilford had been heard predicting hot weather (not unusual in September). Suspicious!

Paranoid Londoners suspected the French or the Catholics had started the Great Fire.

A Frenchman, Robert Hubert was a skilled watchmaker in his mid-twenties who'd worked in London before. In September 1666 he was returning to France after visiting Sweden when his ship was diverted into the Thames.

A foreigner and an oddball who attracted attention, Hubert arrived in Romford on 11 September. He announced he was heading for the coast to find a ship home - and boasted that he'd started the Great Fire.

Thrown into Havering's gaol (located at the west end of Romford Market), Hubert was examined by local magistrate Carew (pronounced Cary) Harvey Mildmay, who lived at a mansion called Marks in Whalebone Lane North, Collier Row.

Aged about 70, Mildmay had fought for Parliament in the Civil War, but had switched to Charles II when the monarchy was restored in 1660. He played safe, and sent the strange Frenchman under arrest to London.

Robert Hubert was obviously a troubled person, seeking attention by confessing to a crime he couldn't have committed.

His story kept changing. He described the place where the Great Fire had broken out - no surprise as everybody was talking about it - but he claimed to have thrown a firebomb through a window that didn't exist.

Later, it emerged that his ship had reached the Thames two days after the Fire had started.

But Hubert was a convenient scapegoat. Thomas Farriner insisted on his guilt - for Farriner owned the Pudding Lane bakery that the Frenchman claimed to have firebombed.

If the Great Fire wasn't caused by arson, then people might blame the careless baker.

Londoners had been looking for a French Catholic terrorist. The problem was that Hubert was a Protestant, a member of France's Huguenot minority. (That probably explains his visit to Protestant Sweden.)

Put on trial in October, Hubert pleaded not guilty, but his "confession" was used as evidence against him. In fact, it had become vital for Londoners to hang him.

The law said that if a rented building was destroyed by fire, the tenant, not the landlord, was responsible for rebuilding.

Our modern insurance industry is largely a by-product of the Great Fire. In 1666, contracts required tenants to keep paying rent and make good the damage - but many of them had lost everything in the flames, and nobody had fire insurance.

But there was a loophole. Tenants would be off the hook if the Fire was caused by enemy action. That meant curtains for Robert Hubert.

On October 27, he was publicly hanged at Tyburn, near today's Marble Arch. When his corpse was lowered the gallows, a vengeful crowd tore it to pieces.

On November 5, the government announced that the French had caused the disaster, and landlords must pay to rebuild London.

It's a problem for police today that disturbed individuals confess to terrible crimes. Sensible people in 1666 knew Hubert was innocent: the historian Lord Clarendon called him "a poor distracted wretch, weary of his life".

By talking wildly in Romford, he made himself a convenient sacrifice to public anger.