Promoting the Sanctity of Life and the Sanctity of Marriage/Family/Human Sexuality (6/8/23 update: Tobiah and his wife, Sarah)
[Duff was a] civil servant and cycling enthusiast....close enough to Irish history to have served as Michael Collins' secretary. A "Pioneer", Frank Duff seems to have been instrumental in preserving the memory of Matt Talbot. Largely introduced to Dublin's poverty and social ills by the St. Vincent de Paul Society, Frank Duff's deep, deep love for God and His Mother led to his being instrumental in founding the Legion of Mary.
....Deeply prayerful and faithful to his religious practice, he also showed his love for God and His Mother through phenomenal apostolic endeavors....
As the life of "Servant of God" Frank Duff is in the early stages of investigation for canonization, his thoughts and writings will certainly receive very close examination.
(My own 10/23/2010 Amazon review of "Frank Duff: Founder of the Legion of Mary")
Before his death in 1990, Uncle Andy told me of how Dublin's early 20th century streets were filled with prostituion. In his time, Duff had an enormous positive impact on that situation.
Long before Vatican II, Frank Duff exemplified the role of Catholic laity in evangelizing the world for Christ.