Victor Stater, in your introduction you describe the Popish Plot as ‘preposterous’. Are we talking QAnon levels, or a more sane conspiracy theory such as the assassination of JFK?

I’d say there are elements of both—the idea that Charles II might be assassinated in order to put his Catholic brother on the throne was certainly plausible. But as Titus Oates and his fellow informers elaborated their tales more and more absurdities crept in:  Queen Catherine’s personal participation in the plot, a 50,000 strong Catholic uprising intending a general massacre of Protestants, the burning of London, invasions by (take your pick) a French army or an Irish Catholic army. None of these claims were remotely plausible.

The country had recently been through a civil war and the interregnum, before restoration in 1660. Did this make the population particularly fertile ground for a conspiracy theory?

The divisions of the civil war were crucial in the evolution of the plot and people’s reactions to it. Although the Restoration was almost 30 years in the past when Tonge and Oates appeared on the scene, former Royalists and Parliamentarians had neither forgotten nor forgiven the events of the civil wars. It was no coincidence that the most fervent believers in the plot’s reality were mostly ex-Parliamentarians (or their descendants) or that the first skeptics were to be found among former Royalists.

The conspiracy was started by two rather eccentric gentlemen, clergyman Israel Tonge and vagabond Titus Oates. What sort of men were they?

Tonge was in many ways a pitiful figure; his promising academic career foundered when Cromwell’s College at Durham shut down after the Protector’s death. The destruction of his parish church in the Great Fire of 1666 seems to have unhinged him. His paranoia about the Jesuits, whom he blamed for his misfortunes, bloomed. His mental instability became increasingly evident, and he died in 1680 having been completely overshadowed by Oates. Titus Oates, by contrast, was a rogue practically from birth. His life was checkered by fraud, perjury, and pederasty. He had no conscience and no shame to the end of his days.

Just how anti-Catholic was the population of 1678?

Anti-Catholicism had deep roots among English Protestants, who learned about Popish cruelty and treachery from infancy on: the massacre of St. Bartholomew’s day, the Gunpowder Plot, the Irish rebellion of 1641 were only the best known incidents. There was a degree of complacency among Protestants in the 1660s and 1670s, but discoveries made of the catholic underground as the plot was investigated brought latent fears to the surface once again.

You’ve described Charles II as ‘Britain’s first modern monarch.’ Why is that?

Charles might be seen as ‘modern’ in a variety of ways. He was a patron of science, chartering the Royal Society and founding the Royal Observatory in Greenwich. He maintained his own lab to conduct chemical experiments. His foreign policy prioritized trade and commerce, rather than dynastic considerations. He established a committee of the Privy Council charged with advancing English trade. He was tolerant on religious questions—he pardoned Quakers and welcomed Huguenot refugees fleeing France. He attempted (but failed) to allow nonconformists and Catholics alike to worship freely. And he embraced—albeit reluctantly—the political revolution that would become two-party politics.

Many innocent catholics were killed. Does that make the ‘plot’ the most lethal conspiracy theory in history?

Perhaps there have been other, more lethal conspiracy theories elsewhere, but I can think of none with more impact in British history, both in terms of lives lost and the longer-term consequences.

Politicians don’t come out of this very well, but the monarch does – is that fair?

I think so; Charles II unquestionably had his faults—he was often inattentive, frivolous and inconstant. But he was not unjust and he was not, like so many politicians of his time, ruthless. He had no taste for persecution and did what he could to defend some of those unjustly accused in the plot. He had mixed success, because he knew that acting too decisively against the informers was politically impossible.

One result of the ‘plot’ was the two-party system. Are we still living with its legacy today?

I think so; two party politics still remain central in much of the English speaking world. Third parties—think the Liberal Democrats or New Democrats in Canada—still struggle to be relevant nationally.

Victor Stater is the author of Hoax: The Popish Plot That Never Was, published by Yale University Press.