Hello Dr. Plant, In just speaking to Douglas Richardson (author of Plantagenet Ancestry), and the controversy of the Warren lines here in America, specifically of William Warren immigrant to Surry VA before 1631,and Humphrey Warren, immigrant to MD, both are displaying y-dna of the I1 haplogroup but are not a match.
I can trace William Warren's line back to abt 1490. Our Humphrey Warren line is suggested to be a direct line from Edward de Warenne and Cecily de Eton but has not yet been proven.
Mr. Richardson is also very interested in this question as well. With your dna interest in your Plant line, he suggests that if you are aware of any dna participants on the Cornwall, Beauford, and or Sommerset lineages, that IF one of any of these males (who are also descendants of the Hamelin/Isabel de Warenne, Plantagenet line), match with either the y-dna results from William Warren OR Humphrey Warren on the Warren y-dna project, that could be a beginning to identify which line is the Warren line off Edward de Warenne ((1316).
Any assistance would be greatly appreciated.
Donna Crosby (I1-John Warren died 1826, Lincoln KY)