New research has uncovered how Londoners reacted in real time to the Great Plague of 1665, revealing that people reshaped their daily lives around published death figures – using them to decide where to go, who to meet, and whether to remain in the city or flee.
The study, from the University of Portsmouth, shows that weekly death reports, known as the Bills of Mortality, served as a practical guide to survival. Rather than being distant or abstract statistics, the numbers directly influenced behaviour, becoming an early form of public health data used by individuals to assess personal risk.
Drawing on Samuel Pepys’s diary, the research illustrates how these figures also transformed the relationship between citizens and the state. Rising death counts were used to justify extraordinary government measures, including quarantine, travel restrictions, and the suspension of everyday freedoms, marking a turning point in how public health was managed.
This day, much against my Will, I did in Drury-lane see two or three houses marked with a red cross upon the doors, and ‘Lord have mercy upon us’ writ there – which was a sad sight to me, being the first of that kind that to my remembrance I ever saw. (7th June 1665).
The findings provide a rare, ground-level view of how people lived through a public health emergency centuries before modern medicine, and reveal striking parallels with how data is used today during health outbreaks to shape both policy and personal decision-making.
“Pepys wasn’t just recording history, he was using death figures to decide how to live,” said Professor Karen McBride of the University of Portsmouth. “His diary shows us, week by week, how published death numbers shaped fear, behaviour, and trust in government. It’s one of the earliest examples of data being used to manage both populations and personal risk.”
Although the year 1665 saw the worst of the plague (total deaths in the Bills in 1665 numbered 97,306, compared with a total of 12,738 in 1666), Pepys continues to comment on the figures and the Bills “with great joy I received the good news of the decrease of the plague this week to 70, and but 253 in all; which is the least Bill hath been known these twenty years in the City. Through the want of people in London is it, that must make it so low below the ordinary number for Bills”
Reading that takes us back to the Covid pandemic and the sense of relief many of us felt when we saw those dreadful death charts on the news start to show a sustained dip, suggesting the worst was finally over.
However, the study also highlights how access to information amplifies inequality.
Wealthier Londoners, including Pepys, could interpret the figures and escape the city, while poorer residents – often living in overcrowded, unsanitary conditions and with less access to information – were more likely to stay in London, simply because they didn’t know they should move elsewhere to avoid infections.
(of course as we now know, moving around would likely spread the plague, hence the lockdowns in the recent pandemic)
Overall, the research challenges the idea that data-driven public health is a modern invention, showing instead how counting deaths became a powerful social and political tool. It also raises enduring questions about how societies balance protection, authority, and personal freedom during times of crisis.
“This research reminds us that debates surrounding accounts and accountability, trust and public freedom are not new. They were already playing out on the streets of 17th-century London.” – Professor McBride.
The research paper has been published in Accounting History.
