Gilles de Duremort, Aegidius Duraemortis, Benedictine, most frequently referred to as the abbot of Fécamp, was a Cistercian monk of Beaubec and bachelor formé in theology when he was named abbot of Beaupré in 1403. Licentiate in theology in 1408 he became abbot of Beaubec in 1413; he was named abbot of Fécamp in 1423 and master regent of the Faculty of Theology at Paris, an office he held until about 1429.

He became Bishop of Coutances in 1439. Gilles de Duremort died at Rouen on July 29, 1444, and was interred in the church of the priory of Saint Lô, which pertained to his diocese.

Gilles de Duremort was a man of considerable importance, and resided chiefly at Rouen, sometimes in the great hotel de Fécamp, sometimes in his hôtel in the parish of Saint Vincent. He had long enjoyed the entire confidence of the English government when in June, 1421, he was commissioned to intervene in favor of the University of Paris before Henry V. The Duke of Bedford sent him on an embassy in Burgundy to pacify the quarrel between Gloucester and the duc de Brabant in 1424.

Gilles de Duremort went many times to England and to Burgundy before 1426.
In 1427 he went on an embassy to Brittany. Appointed councilor of the English king, with the considerable salary of 2,000 livres, he took the oath of office in 1428.

In 1429 Gilles de Duremort went to England on matters of state. In 1431 he was entrusted with the embassy to the Council of Bile. On November 16th of that year, Henry VI ordered the Treasurer-general, Thomas Blount, to pay the wages of ten lancers and thirty mounted archers who escorted the abbots of Fécamp and Mont Saint Michel and the Lord of Saint Pierre, who were summoned to Paris by the king.

In 1438 he was designated as the ambassador of Henry VI to treat for peace with the King of France; on July 5, 1439, he was given 300 livres and sent on an embassy to Calais; in 144o he was given 250 livres from the English treasury as a quarter of his salary.

Gilles de Duremort was strongly allied with the Cardinal de Luxembourg, who named him among the executors of his will. He was one of the most assiduous judges at Jeanne's trial, and upon the testimony of Jean Massieu himself, this regent in theology "seemed oftener to act through hatred of Jeanne and through love of the English than through zeal for justice."

In the session of May 29th Gilles de Duremort formulated the opinion, or rather, the death sentence, in which the assessors lost no time in joining him, without lengthy explanations.