Martin Lings, also known as Abū Bakr Sirāj ad-Dīn, was an English writer, scholar, and philosopher who wrote biography of Holy Prophet Muhammad PBUH titled as “Muhammad: His Life Based on the Earliest Sources”. Most websites have Michael H Hart as correct answer on them but that is completely wrong amswer. Michael H Hart has authored “The 100: A Ranking of the Most Influential Persons in History” which had placed name of holy prophet at top in his list but he did not write biography of holy prophet.