Fr. David Knowles, OSB, FRHistS was born Michael Clive Knowles and was given the name 'David' when he joined the Order of Benedict in 1923. He was a historian and professor at University of Cambridge from 1947 to 1968 and served as president of the Royal Historical Society from 1957 to 1961.
*Note: there is more than one author named 'David Knowles,' however this particular individual is the most widely published.