One of these was Queen Brunhildis. Desiderius found the behavior of her courtiers shameful, and said so. The queen appealed to Pope Gregory the Great, accusing the bishop of being too much interested in the writings of pagans. Pope Gregory remonstrated with him for personally giving lessons in so profane a subject as grammar--Latin grammar. (Gregory also wrote to Desiderius to request hospitality for Saint Augustine of Canterbury on his way to England from Rome.)

For several years the bishop was banished but eventually Gregory the Great came to see that he was innocent of Brunhildis's charges and restored him to Vienne. Desiderius also attacked the queen's grandson, King Thierry II of Burgundy, whose life was as immoral as his grandmother's. Thierry found a new false charge to bring against Desiderius: He alleged that Desiderius had an immoral relationship with a lady named Justa. In consequence, Desiderius was banished from his diocese for some years.

On his return from exile, he was soon in trouble again for having rebuked King Thierry for his shameful life. As he was being taken into detention, three of his escort set on him (at a place now called Saint-Didier-sur-Chalaronne) and cruelly murdered him, apparently on the initiative of the soldiers rather than by order of Thierry.

Desiderius is venerated as a martyr because he was put to death in the execution of his duty as a bishop (Attwater, Benedictines, Bentley).

John entered the Roman College at 13. He completed the classical course of studies but began practicing severe mortifications after reading an ascetical book. Their severity, combined with a heavy course load and a bout of epilepsy, led to a breakdown, and he was forced to leave the college. He recuperated and completed his training at Minerva but was never again very strong.

At age 23 (1721) he was ordained, and he celebrated his first Mass in the Roman College. He had visited hospitals as a student, and now he focused his attention upon them. He concentrated especially on the hospice of Saint Galla, an overnight shelter for paupers that had been founded by Pope Celestine III. He divided his labors among Saint Galla's, the hospital of the Trinita dei Pellegrini, and serving the people of the area.

John combined the enfleshment of the social Gospel with the cure of souls. He catechized teamsters, farmers, and the cattlemen from the country who came to the marketplace, and he sought to help homeless women and girls who lived in the streets, beggars and prostitutes. He was penniless except for paltry Mass stipends, but with a local donation and a donation from the pope, he rented a house behind the hospice and made it a refuge, placing it under the protection of Saint Aloysius Gonzaga.

Later, his cousin obtained for John the position of assistant priest at Santa Maria in Cosmedin at the foot of the Aventine. The church had not been well-attended, but John now drew throngs of penitents of all classes to his confessional. He was so sought after as a confessor that he was released from his choir obligation. When his cousin died in 1736, the canonry was given to John, who used the compensation from the office to buy the church an organ and to pay an organist. He chose to live in an attic, giving the house that had been his legacy from his cousin to the chapter.

Pope Benedict XIV chose John to instruct prison and other state officials, including the public hangman. His preaching was in great demand, and he was often asked to give addresses in religious houses.

His body was found by a madwoman who garlanded it with honeysuckle, and through it was cured of her insanity. As a result of this and other miracles wrought at his intercession after death, he was acclaimed a martyr by the people and his body was enshrined in the cathedral of Rochester. First it was in the crypt, then in the north-east transept, where offerings at his shrine contributed towards the rebuilding of the church.