He stayed in London during the Revolutionary War, representing the colonies to Britain and France and also serving as an American spy to track their activities.

The title description of his thesis is: Dissertatio medica inauguralis, de cortice peruviano: quam ... ex auctoritate ... Gulielmi Robertson ... Academiae Edinburgenae praefecti ... pro gradu doctoratus ... eruditorum examini subjicit, Arthur Lee, Virginiensis.

[9] During this time in London, Lee wrote many influential pamphlets and essays opposing slavery[10] and British continental policies.

Lee criticized Franklin's extravagant lifestyle and told Sam Adams he would never be a good negotiator between a free people and a tyrant.

In May 1776, he was a guest at the dinner organized by publisher Charles Dilly that—at the urging of James Boswell—brought together Samuel Johnson, an ardent opponent of the American colonists' cause, and John Wilkes, one of its most prominent British supporters.

[12] During the American Revolution, the Continental Congress appointed Lee as its envoy to Spain and Prussia, but his success was at best mixed.

[9] Later, in Paris, after Lee helped negotiate the Treaty of Alliance (1778) with France, he fell out with Benjamin Franklin and Silas Deane.

[7] He earned a reputation of being overly suspicious where, Franklin, in a letter of April 3, 1778 chided him that if he let these feelings dominate his life that he would end up insane.

[15] He unsuccessfully ran as the Anti-Administration candidate for Virginia's 4th congressional district in 1790, losing to incumbent Richard Bland Lee, a distant relative.

[16] He was also a candidate in the October 1792 special election for the U.S. Senate seat previously held by Richard Henry Lee, another distant relative, but he lost to John Taylor of Caroline.