The fire started in a bakery on Pudding Lane in the early hours of 2 September 1666 and burned for four days. When it stopped it had taken about thirteen thousand houses, eighty seven parish churches, the Royal Exchange, the Guildhall and old St Paul’s Cathedral, and left roughly four fifths of the walled City as rubble and ash.
Within a week, three men had drawn plans for a new London on paper. None of the plans was built. What actually rebuilt the City was a slower and far less glamorous piece of work, and the man who did most of it spent the following decade walking around with measuring poles, settling arguments between neighbours about six inches of frontage.
That man was Robert Hooke, who is usually remembered for a microscope and a law about springs.
The Plans That Went Nowhere
Christopher Wren presented a plan to Charles II within days, a design of broad avenues radiating from piazzas in the Roman manner. John Evelyn produced another. Hooke had a scheme ready in about the same week, and on 19 September the City Corporation looked at his proposal for a rectangular grid of streets and formally approved of it.
Nothing came of any of them, and the reason had nothing to do with architecture.
London was not owned by the King or by the Corporation. It was owned in thousands of separate freeholds and leaseholds, many of them with documents that had just burned. Redrawing the street plan meant extinguishing every one of those interests and reassigning them, in a city whose merchants needed to be trading again before their trade moved permanently to Bristol or Amsterdam. The legal work alone would have taken a generation.
So Parliament chose speed. The Rebuilding Act of 1667 kept the medieval property boundaries almost intact and regulated what could be built on them instead.
- Brick or stone only. No more timber framing with overhanging upper floors, which had let the fire cross streets at roof level
- Four standard classes of house, fixed by the width of the street they stood on, with the storey heights and wall thicknesses written into the statute
- Widened and straightened streets, paid for by taking small strips from the affected plots, with compensation assessed case by case
- A tax on coal entering the port to fund the public buildings, which is how the churches and the Monument were paid for without a general tax
It is one of the first building codes in the modern sense: not a design, but a set of constraints that anyone could build within. It also created an enormous amount of surveying.
The Job Nobody Wanted
The City appointed three surveyors to carry the Act into practice. Hooke was one of them, alongside Peter Mills, and later John Oliver and Edward Jerman. Wren, appointed by the Crown, handled the cathedral and the parish churches. The City surveyors handled everything else, which meant the private houses, and there were thousands of them.
The work was physical and repetitive. A citizen who wanted to rebuild had first to have the old foundations staked out and certified. Hooke went to the site, measured the plot against whatever evidence survived, drove in the markers, and signed the certificate that allowed building to start. His diary records days of six, eight, ten stakings out.
Then came the disputes, which went to a special Fire Court set up to settle them without the delays of ordinary litigation. Two neighbours would both claim the same strip of ground, or a landlord and a tenant would disagree about who should pay to rebuild. The court needed a measured answer, and the surveyors supplied it.
Hooke did this for something like a decade. He was paid well for it, and for the first time in a life that had begun with him working as a servant at Oxford to pay his fees, he had money. When he died in 1703 a chest in his room at Gresham College held several thousand pounds in coin, much of it apparently untouched since the rebuilding years.
The Monument Is a Telescope
The Act required a column near the site where the fire began, and Wren and Hooke designed it together. It is a fluted Doric column of Portland stone, 202 feet high, standing 202 feet from the bakery in Pudding Lane, and it is the tallest isolated stone column in the world.
It is also, and this is the part that gets left out of the guidebooks, a piece of scientific apparatus.
The shaft is hollow, with a spiral staircase around a central void. There is a laboratory in the basement, connected to the void by a hinged opening, and a hinged lid at the very top on the axis. Open both and the column becomes a zenith telescope two hundred feet long, pointing straight up.
Hooke wanted it to measure stellar parallax. If the Earth moves around the Sun, a nearby star should shift its apparent position slightly against the more distant ones over the course of a year, and measuring that shift would settle the Copernican question by direct observation. A very long vertical instrument avoids the distortion of looking through air at an angle, which is exactly why the shape appealed to him.
He had already tried the same experiment through a hole in the roof of his lodgings, using the star Gamma Draconis, which passes almost exactly overhead in London. He believed he had found a parallax. He had not. The shift he was chasing is under one second of arc for even the nearest stars, and it defeated everyone until Friedrich Bessel measured it properly in 1838.
The Monument failed as a telescope for a more mundane reason as well. It stands on a busy street, and the traffic shook it. The staircase was used instead for barometric and pendulum experiments, taking readings at the top and at the bottom of a known height, work that descends directly from Torricelli’s column of mercury and the question of how far the atmosphere extends.
The Hanging Chain
The rebuilding also produced the most elegant thing Hooke ever wrote, and he published it as a riddle.
At the end of a book on helioscopes in 1676 he printed a list of inventions he wanted to claim without revealing, encrypted as anagrams. One of them decodes to a single Latin sentence: Ut pendet continuum flexile, sic stabit contiguum rigidum inversum. As hangs a flexible cable, so, inverted, stand the touching pieces of an arch.
Hang a chain from two points and it settles into the curve that carries its own weight in pure tension, with no bending anywhere along it. Turn that curve upside down and build it in stone, and you have the shape that carries its own weight in pure compression, which is what masonry is good at. It is the correct answer to the central question of building in stone, arrived at with a piece of string.
Hooke never published the solution, and the curve itself, the catenary, was worked out mathematically by Johann Bernoulli, Leibniz and Huygens in 1690 and 1691 in response to a public challenge. But the principle was in use at St Paul’s while the mathematics was still being argued about. The cathedral’s dome is three shells, and the hidden middle one, the cone of brick that actually carries the stone lantern on top, follows very nearly that inverted hanging shape.
The same physics runs through Hooke’s law of elasticity, published two years later in 1678 and also first released as an anagram. Both are answers to the same question, which is how materials behave under load, and both came out of a decade spent watching a city being put back up.
Who Designed What
Hooke’s own buildings included the Royal College of Physicians, Montagu House in Bloomsbury, which later became the first home of the British Museum, and Bethlem Hospital at Moorfields, a long symmetrical palace front that became notorious under its shortened name of Bedlam.
The harder question is how much of Wren’s work is also his. They were close friends who met constantly, and the drawings that survive are frequently in Hooke’s hand for buildings credited to Wren. Several of the City churches are now attributed wholly or partly to Hooke, and the structural solution of the St Paul’s dome is a running argument among architectural historians.
What is not in doubt is that the partnership suited Wren’s reputation better than Hooke’s. Wren had a knighthood, a court appointment and one enormous famous building. Hooke had a surveyor’s certificate book and, for the last twenty years of his life, a feud with Isaac Newton that did his posthumous reputation no good at all.
What It Cost Him
There is a version of this story in which the rebuilding is a tragedy, ten years of science lost to municipal paperwork by the man who had published Micrographia the year before the fire and might have gone on to anything.
It is worth resisting. The decade of surveying is where Hooke’s structural mechanics comes from, and the Monument is what happens when a Curator of Experiments is handed a construction budget. He was not doing administration instead of science. He was doing the kind of science that has to be right the first time, because a wall built on a wrong line does not get a second draft.
The city that stands inside the old walls today still follows the medieval plot lines he staked out, which is why the streets of the City of London wander the way they do while the buildings on them are perfectly regular. It is the largest surviving object Hooke worked on, and almost nobody walking through it knows whose measurements it is standing on.
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