I too descend from William and Prudence Lankford Clayton, in my case through their daughter Honour who married James Brown. An article by James E. Bellarts (1931-1994) in "The Southern Friend: The Journal of the North Carolina Friends Historical Society" shows how Clayton's royal ancestry, and connection to the Joshua Clayton family, as well as other prominent Clayton families, was debunked. I can photocopy it and send it to you if you are unable to access this periodical. I have seen mention of how our William has been mixed up with another William Clayton, which has made me want to prove that our William was indeed Acting Governor of Pennsylvania in 1684-85. I have not tried to solicit the opinion of the Society of Descendants of Colonial Governors yet to determine whether William would qualify me for membership.