Isaac Newton: 17th-Century London’s Dirty Harry

The science titan wasn’t used to being outsmarted. But after two years of trying to shut down English counterfeiting, one underworld kingpin was still getting the better of him.

Back in 1695, England’s Royal Mint discovered a serious problem: A massive portion of the circulating currency was phony. As counterfeiting methods grew increasingly clever, the Mint turned to England’s brightest mind for a solution. Isaac Newton was appointed Warden of the Mint, a one-man army who waded through London’s underbelly to restore the currency’s integrity. Most counterfeiters were easy prey for Newton, but William Chaloner, a shadowy kingpin, kept eluding his grasp.

Chaloner had trained as a nail maker’s apprentice, but he found a more lucrative application for molten metals: coining 30,000 guineas. The counterfeiter’s self-made wealth enabled him to pose as a gentleman and gave him an ego to match his intellect.

Newton wanted nothing more than to destroy Chaloner, and the feeling was mutual.

Chaloner appeared before a parliamentary committee, where he insinuated that Newton was incompetent and blamed Mint employees for the epidemic of phony coins. Enraged, Newton intensified his efforts.

When Chaloner set up a coining facility in Egham, 20 miles outside of London, Newton sensed an opening. He began studying Chaloner’s sophisticated casting method—which involved pouring molten metal into brass molds before filing down the molds’ faces, resulting in much sharper images on the phony coins.

By September 1697, Newton had enough evidence to lock Chaloner up—but not for long. Working through intermediaries inside the prison and out, Chaloner bribed the prosecution’s star witness into fleeing to Scotland. Chaloner was released and accused Newton of framing an innocent man.

After nearly two more years of relentless pursuit, Newton’s extreme measures had gathered enough evidence to put Chaloner away for good. This time, the charges stuck. On March 3, 1699, the counterfeiter was found guilty of high treason. The next day he was sentenced to hang. In the days before the execution, Chaloner wrote Newton a long, rambling letter proclaiming his innocence. The condemned counterfeiter begged his old rival for mercy, writing, “O dear Sir nobody can save me but you.”

Newton felt no pity. He snubbed his rival by not attending the hanging. As Newton had written during Chaloner’s first trial, the counterfeiter had formed “a confederacy against the Warden.” Chaloner could have lived a long, honest life had he “let the money & Government alone.”

With Chaloner dispatched, Newton torched the records of his investigation, likely to cover up the murky steps he took to help save the pound. In 1703, he gave up crime fighting and returned to academia as president of the Royal Society. England’s currency was once again safe from scoundrels like Chaloner, and criminals and thinkers alike had learned a valuable lesson: You don’t mess with Isaac Newton.

This story originally appeared in mental_floss magazine. Now go download our new iPad app! Or get a free issue of mental_floss magazine via mail.