The parish arose beside the old manor of Diedegem, probably soon after Kornelimünster received the estate. The abbey itself appointed the priests; in the 14th and 15th centuries these were men such as Lambert van Aken, Herweyn Utenhove and Daneel Daneels, who also managed the abbey's tithes. Only on 19 December 1605 was this special arrangement ended, and from then on the archbishop of Mechelen appointed the parish priest. A first church is mentioned in 1379, when a messenger from Leuven found asylum there from the anger of his city's patricians.
A new church
The oldest parts of the present church, the four piers of the tower, date from around 1400. Brussels was then a prosperous city, and the building boom spread to the surrounding area. Diegem could keep up: in 1435 it had 109 houses, more than Machelen (89), Zaventem (88) or Haren (30). The choir and the north transept followed in the 15th century, the nave in the first half of the 16th; the wars under Maximilian of Austria slowed the work. It is Brabant Gothic, without flying buttresses or ambulatory, but with a striking unity, although it took more than a century to build.
Celebration in 1543
The church accounts of 1543 show that the church was finished by then. From 1541 the south porch was converted into a pilgrims' house, using sandstone from the Kleet. Entirely new furnishings came from Brussels and Mechelen: seven altars with ironwork by Jan de Greve, painted by Jan Lambrechts, a font and new lecterns. For the dedication a procession of Saint Cornelius went through the village, with the trumpeters and city musicians of Brussels, Brabant guilds and a St Anthony float. The St Anthony guild of Merchtem won first prize. The church paid for 100 eggs for Easter night, 270 for Easter Day and half a calf.
The inventory of 1639
In 1639 parish priest Joannes vander Eycken drew up an inventory. The church had three bells of about 3,000, 1,800 and 700 pounds, a clock, two organs and seven altars: the high altar of Catherine, Our Lady and Cornelius in the transepts, and in the nave St Anne, St Hubert, the Four Crowned Martyrs and the Sweet Name of Jesus. On the right of the choir stood a sacrament tower of white stone with delicate figures, reaching almost to the vault. It later disappeared; two fragments still lay in the presbytery garden, and the statuette of St Benedict in the niche of the Cornelius altar probably comes from it.
Wall paintings
In 1895, when the whitewash was removed inside the church, 16th-century figures of apostles appeared on the piers; Paul, Thomas, Thaddeus, Peter and John could still be made out. The minister asked for them to be carefully preserved, but the church council found a full restoration too expensive, and a trial restoration was disappointing. Parish priest Juul Lapage (1955-1958) discovered a well-preserved Crucifixion under several layers of whitewash in the old sacristy. Above the capitals you can see slots that once held iron bars for hanging tapestries on feast days.
Portals and pilgrims' house
Three portals gave access to the church. The west door, used for funerals, and the north door closely resemble the main portal of Anderlecht. The tympanum of the north portal shows Cornelius, with a smaller Catherine and Roch beside him. The south porch was a pilgrims' house with an upstairs room where pilgrims could spend the night. There was no staircase: you climbed a ladder to a door about 5 metres up in the church wall, which was bolted from the outside. In 1674 the doorway was walled up, and in 1775 parish priest Forneville turned the porch into a baptistery; at the same time a new sacristy and the ‘henhouse’ were added.
In wartime the church rented out its attics, the pilgrims' house and the wood shed as storage for grain and household goods. The conditions of 1746 survive: rental for one year, no more than 15 sacks of grain above the nave or the choir, and access only twice a week. The poor table also stored its grain for the poor there.
Repairs
The church was repaired in 1887 (tower), 1888 and 1895, and listed as a whole on 25 March 1938. Bombing of the nearby airport during the Second World War badly damaged the roofs, windows and vaults. After years of letters, permission for the repairs came only on 3 March 1954, with 1.2 million francs of state aid. Parish priest Juul Lapage saw the full restoration completed. In 1972 the church square was paved.