Was Edward Bancroft a British double agent who fooled not only John Paul Jones but also Benjamin Franklin?
American leaders hoped to embroil Britain in a war against other foes (specifically, an alliance of France and Prussia), which they hoped would distract Britain. Bancroft was unenthusiastic about American independence, and the possibility of a French war against Britain alarmed him; hence he decided to spy for Britain. Simultaneously, Bancroft pretended to spy for the Americans Silas Deane and Benjamin Franklin (Wikipedia, “Edward Bancroft”).
Bancroft reported to the British under the cover of weekly letters to “Mr. Richards,” signed “Edward Edwards,” about “gallantry” (exploits with the ladies). But between the lines of the cover text, Bancroft wrote his reports in a special ink. Every Tuesday after 9:30 PM, he put the letter in a bottle, tied a string around it, and left it in a hole in a certain box tree in Paris. A British official retrieved the message and replaced it with new orders. Bancroft would return later that night to recover the bottle. Through this method, George III may have seen the French-American Treaty of Alliance just two days after it was signed (Wikipedia, “Edward Bancroft”).
When Arthur Lee accused Bancroft of being a traitor, U.S. Navy Captain John Paul Jones came to his defense (Wikipedia, “Edward Bancroft”).
There is some suggestion by historians that Franklin was aware of Bancroft’s betrayal, citing Franklin’s comment in response to a friend’s warning about British spies (https://fas.org/irp/ops/ci/docs/ci1/ch1c.htm):
“I have long observ’d one Rule which prevents any Inconvenience from such Practices. It is simply this, to be concern’d in no Affairs that I should blush to have made publick, and to do nothing but what Spies may see & welcome. When a Man’s actions are just and honourable, the more they are known, the more his Reputation is increas’d and establish’d. If I was sure, therefore that my Valet de Place was a Spy, as probably he is, I think I should not discharge him for that, if in other Respects I lik’d him.”
Although some historians believe the letter indicates Franklin’s suspicion of Bancroft, others have noted that after the war, Franklin remained on good terms with Bancroft while he shunned other Loyalists, including his own son, William (Wikipedia, “Edward Bancroft”).
Bancroft’s activity as a double agent was not revealed until 1891, when British diplomatic papers were released to the public (Wikipedia, “Edward Bancroft”).
As a sidenote, how did Revolutionary War spies communicate? While serving in Paris as an agent of the Committee of Secret Correspondence, Silas Deane is known to have used a heat-developing invisible ink, compounded of cobalt chloride, glycerin and water, for some of his intelligence reports back to America (https://fas.org/irp/ops/ci/docs/ci1/ch1c.htm).
Even more useful to him later was a “sympathetic stain” created for secret communications by James Jay, a physician and the brother of John Jay. Dr. Jay used the “stain” for reporting military information from London to America. The stain required one chemical for writing the message and a second to develop it, affording greater security than the ink used by Deane earlier. Later Jay supplied quantities of the stain to George Washington at home (https://fas.org/irp/ops/ci/docs/ci1/ch1c.htm).
Washington instructed his agents in the use of the “sympathetic stain,” noting in connection with “Culper Junior” that the ink “will not only render his communications less exposed to detection, but relieve the fears of such persons as may be entrusted in its conveyance .. . .” Washington suggested that reports could be written in the invisible ink “on the blank leaves of a pamphlet . . .a common pocket book, or on the blank leaves at each end of registers, almanacs, or any publication or book of small value.” Washington especially recommended that agents conceal their reports by using the ink in correspondence: “A much better way is to write a letter in the Tory stile with some mixture of family matters and between the lines and on the remaining part of the sheet communicate with the stain the intended intelligence” (https://fas.org/irp/ops/ci/docs/ci1/ch1c.htm).