From the beginning, the monastic school became famous, and the abbey flourished; the monks founded the monastery of Lubin in Poland, as well as the priory of Saint-Léonard in the northern district of Liège.

The abbey church housed the tomb of a foreign bishop named John: a sarcophagus with a recumbent effigy in tuff, dressed in pontifical vestments, with his head under a canopy and feet under a console.

[1] The Saint James Abbey was secularized by Pope Pius VI on 28 May 1785, and transformed into a collegiate church for twenty-five canons.

The second major restoration took place between 1972 and 1975; archaeological excavations at that time uncovered the remains of the Romanesque crypt and the foundations of the original church.

[4][5] The stained glass windows of Saint-Jacques are considered by some authors to be perhaps the most beautiful in Belgium,[6][7] the French archaeologist Adolphe Napoléon Didron even ranks them as the best among all surviving from the 16th century.

The entire scene is surrounded by sixteen heraldic shields representing the donor’s paternal and maternal lineage; in the upper part and the interlaces, Christ and angels bear attributes.

The next stained glass window was donated in 1531 by Richard de Mérode and Arnould le Blavier, burgomasters of Liège.

The central window was donated by Jean de Cromois, abbot of Saint-Jacques from 1506 to 1525; it depicts the sacrifice of Calvary, that of Isaac, and the Bronze Serpent, both of the latter being prophetic of the Cross.