Edward Bancroft Edward Bancroft ( 9 January 1744 – 8 September 1821 ) was an American physician and double - agent spy during the American Revolution . Bancroft worked as a spy for Benjamin Franklin in Britain before the Revolution , and while serving as secretary to the American Commission in Paris . During the latter period , he was also a spy for Britain , reporting on dealings between France and the United States . Early life . Bancroft was born on 9 January 1744 in Westfield , Massachusetts . His father died of an epileptic seizure when Bancroft was only two years old , and his mother had to support the family alone . His mother remarried five years later , and they moved to Connecticut to live with his stepfather , David Bull . In Connecticut , Bancroft studied under Silas Deane , a schoolmaster who later became an important politician and diplomat . At the age of sixteen , Bancroft was apprenticed to a physician in Killingworth , Connecticut , but ran away after a few years . Many years later , Bancroft returned and repaid his debt to his former master . On 14 July 1763 , Bancroft departed the colonies for British Guiana , where he became a doctor on a plantation . He soon expanded his practice to multiple plantations and wrote a study of the local environment . His discovery that the torpedo fish discharged electricity is notable . Bancroft grew tired of South America and left in 1766 . He spent a year traveling between North America and South America before leaving for London . London years . In London , Bancroft studied medicine at St . Bartholomew ' s Hospital . During this period , he also published a book entitled " Natural History of Guiana " ( 1769 ) . This book attracted the attention of Paul Wentworth , New Hampshire ' s colonial agent in London . He hired Bancroft to survey Wentworth ' s plantation in Surinam and make recommendations for more efficient operation . Bancroft spent two months in Surinam at Wentworth ' s plantation before returning to London . He was elected a fellow of the Royal Society in 1773 as " " a gentleman versed in natural history and Chymistry , and author of the natural history of Guiana " " Bancroft now encountered another colonial agent in London , Benjamin Franklin , representative of Pennsylvania . Bancroft and Franklin became friends , and Bancroft agreed to become a spy for Franklin . Spying for Franklin . Bancroft was employed to gather information from British political and military sources for Franklin . It ' s not clear whether Bancroft continued spying after Franklin left London in 1774 . Most agree , nonetheless , that Bancroft maintained his position as an agent for the colonies . When the Committee of Secret Correspondence sent Silas Deane ( Bancroft ' s former teacher ) to France in 1776 , Franklin wrote Deane telling him to contact Bancroft . This suggests that Franklin believed that Bancroft would be a source of useful information for Deane . Deane arrived in France on 7 June 1776 ; the next day he wrote Bancroft , asking him to come to Paris . In the letter , Deane said they would discuss procuring goods for trading with the Indians , and enclosed thirty pounds ( a generous amount ) for travel expenses . Bancroft met with Deane on 8 June , and learned that Deane ' s purpose in France was to win French aid for the Americans against Britain . While Bancroft declined the invitation to attend negotiations , he did serve as Deane ' s assistant and interpreter . Deane ' s negotiations resulted in France sending some supplies to the Americans . Deane told Bancroft that 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 . Though Deane and other Americans thought France would form the alliance , this ploy came to nothing . But it greatly troubled Bancroft . On 26 July 1776 , Bancroft returned to London . Before leaving France , he assured Deane that he would spy for the colonies in Britain . Spying for the British . Though Bancroft had worked for Franklin and Deane , he was not a great enthusiast for American independence , and the possibility of a French war against Britain alarmed him . Despite his promise to Deane , he had reservations about doing anything that might promote a rift between Britain and the American colonies . In London he met Paul Wentworth , recently recruited by the British Secret Service . Wentworth arranged for Bancroft to meet Secret Service chief William Eden and Lords Suffolk and Weymouth . Bancroft agreed to be a double agent for Britain . Soon after this , Franklin arrived to take over the negotiations with France . Bancroft was ordered to associate himself with Franklin . Fortuitously , Franklin appointed Bancroft as secretary to the American Commission in Paris . For his spying , the British promised Bancroft a pension of 200 pounds . ( This amount was later increased to 500 and then 1 , 000 pounds . ) Bancroft reported under the cover of weekly letters to " Mr . Richards " , signed " Edward Edward " , about " gallantry " ( the writer ' s exploits with ladies ) . But between the lines of the cover text , Bancroft wrote his reports in a special ink . Every Tuesday , he put the letter in a bottle , tied a string around the bottle , and left the bottle in a hole in a certain box tree in Paris , after 9 : 30 PM . A British official retrieved the message and replaced it with new orders . Bancroft return later that night to recover his bottle . It is said that , through this method , George III saw the French - American Treaty of Alliance just two days after it was signed . In addition , Bancroft was often sent on spying missions to London by Franklin and Deane , so he was able to report directly to Lord Suffolk and others . Franklin ' s possible knowledge of Bancroft ' s intrigue . There is some debate as to whether Franklin knew that Bancroft was a British spy . Franklin wrote that even though he suspected one associate of being a British spy , as long as he ( Franklin ) did not provide the suspect with any private information , there was nothing to worry about , and the spy need not be dismissed . Even if Franklin did discover Bancroft ' s true loyalty , he never revealed it explicitly in any of his extant writings . Regardless , Bancroft was " successful but ineffective " ; that is , he certainly gathered a good deal of information , but the British did not prevent the French - American alliance . Life after the Revolutionary War . At the end of the Revolutionary War , Bancroft obtained patents giving him the right to import chinkapin ( yellow ) oak bark into Britain and France . He became wealthy from this trade . In 1794 , Bancroft published " Experimental Researches Concerning Permanent Colors " , a book he updated in 1813 . He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1797 . Bancroft ' s activity as a double agent remained hidden until 1891 , when British diplomatic papers were disclosed to the public .