He was born in 1953 in Vienna, his uncle being a Prelate and Pastor of St. Rochus Church in the same city.
In 1976 he decided to become a priest and studied at the Angelicuм in Rome, taking doctoral degrees in theology and canon law.
In 1981 he was ordained in the new Rite of Ordination by Archbishop Aurelio Sabattani in St. Peter's Basilica. Soon, he solely celebrated in the Tridentine Rite himself.
Sometime later he was the secretary of the famous Cardinal Alfons Maria Stickler and worked in the Vatican Secret Archives.
In 1991, he left Rome and became independent. He was associated with "actio spes unica" of Fr. Milch who was the most outspoken German traditionalist until his murder in 1987. The latter organization was and is working together with the SSPX as was Fr. Hesse.
He died in 2006.
Fr. Gregorius Hesse was certainly a colourful, interesting, intelligent and humorous person. Personally, I find many of his opinions untenable and some of his comments downright offensive to pious ears. Still, I would love to find out where he got his ideas from - but I missed my chance.
I am sure most people on this forum have a much more positive view on him.