Although he briefly considered a career in law, he had served as both London correspondent for The New York Sun and as associate editor of the North American Review before he decided to pursue the Catholic priesthood as a Franciscan.

By 1914, the year he was inducted into the Royal Historical Society, he was known as "one of the foremost living historians of the Middle Ages", a specialty he cultivated while at Oxford University.

[4] In 1913, he was appointed Professor of Medieval History at The Catholic University of America in Washington D.C.,[5] a position he held from 1913 to 1919, when the Holy See took him into a diplomatic service in Rome.

[7] In 1934, a photographer captured the German Envoy to Ireland, Georg von Dehn, kissing Robinson's episcopal ring.

[8] Von Dehn was immediately recalled and removed from diplomatic service by Adolf Hitler for unbecoming conduct, and the photograph – and word of its repercussions – spread internationally.