David talks about his mentor in one of the audio books, but doesn't say his or her name...
BTW David Allen is my mentor
One of David Allen's mentors was Dean Acheson.
Originally posted by http://money.cnn.com/magazines/business2/business2_archive/2007/07/01/100117066/index.htm
From Michael the karate teacher, Allen learned the power of an empty mind when confronting new challenges. By running a travel agency, he picked up the idea for a "tickler file," a series of folders labeled by day, week, and month that helps people prioritize tasks. Many of GTD's most important concepts came from a small-business consultant named Dean Acheson, who taught Allen to create a master list of everything that commands his attention and assign a "next action step" for each.