In And by Fire, Detective Inspector Nigella Parker has a fear of fire deeply rooted in her childhood. But even people who generally aren’t pyrophobic would be terrified by the heat generated by London’s Great Fire of 1666—legitimately so.
How hot did things get inside London in September of 1666 when, in just under five days, one-third of the city was destroyed (436 acres, including over 13,000 homes) and approximately 80,000 people were left homeless? You’re going to be sorry you asked.
Sources I consulted while writing And by Fire confidently project temperatures during London’s great fire hit and exceeded 3000 degrees Fahrenheit—at least in areas where the conflagration reached firestorm proportions.
That’s a temperature far in excess of what it takes to melt glass, iron or steel (although there was no such thing as steel in 1666, it melts between 2282 and 2696 degrees Fahrenheit). Bodies in many areas of London—not just the ones that heated to 3,000 degrees—would have disappeared without trace. Because a temperature of “only” 1380 degrees Fahrenheit is required for human cremation. A fact that helps to explain the woefully low and inaccurate count of those killed by the Great Fire that persisted for years (more about that in a later post).
How did it get so damn hot?
A confluence of factors contributed to the hellish and unimaginable heat during London’s Great Fire.
Building materials were part of the equation. Structures in Restoration London were old and highly combustible. A large number of dwellings were timber-framed, Elizabethan style—a type of construction that burned like a tinder box. Pitch—painted on wooden houses to protect them from the elements—became volatile in fire conditions, helping to spread the flames. And interior design turned up the heat as well: “fueled by wainscoting, paneling, paintings, curtains, furniture and hangings, a fire inside a single timber-framed Elizabethan house . . . can generate temperatures in excess of 1,000 Celsius—enough to melt lead, glass, brass, bronze and silver.”1
If London’s structures were powder barrels waiting to burn, the city’s cramped, crowded layout exacerbated the fire-friendly situation—facilitating both spread and high fire core temperatures. The upper levels of many pre-fire structures jutted out over the streets, in some places nearly touching. Streets and alleys were exceedingly narrow—a situation that created a chimney effect (think major updraft), allowing the fire to increase in velocity as it climbed upwards through these constricted spaces.
Then there were the gale force winds. London had been suffering from them for days before the fire started. And once the conflagration was sparked, the gales provided a constant supply of oxygen for the flames. As the fire got big enough in specific areas it began to create its own “convection current” as temperature variations whipped up air-flow. According to my research if one area in a fire-scape is even a few degrees cooler than another, a wind is created, racing from the cooler to the hotter area. And during the Great Fire such temperature differences—estimated to be at least 1800 degrees Fahrenheit between fire cores and the unheated air just beyond the fire’s perimeter—didn’t just create violent winds, they gave rise to “fire tornados” such as those seen in Dresden during WWII. No wonder then that the terrified population of 1666 London, fleeing before the flames, believed they were seeing an act of God’s vengeance! (for more on that read 1666: The Devil’s New Year)
Whipping and spinning tornados of flame, walls of flame rising more than forty feet and racing along at one hundred to two hundred feet per second, temperatures inside burning homes topping 1800 degrees Fahrenheit and heat in the streets reaching above 3,000 degrees in concentrated fire areas—sounds like hell on earth to me.
1 Tinniswood, Adrian. By Permission of Heaven: The True Story of the Great Fire of London p. 98
2 Tinniswood p. 104.