Saint Cornelius was Diegem's oldest patron, introduced by the abbey of Kornelimünster. The oldest documents, from 1358 onwards, always speak of the church of ‘Sinte Cornelis tot Dieghem’, and the deans also name him as patron from 1509. Before 1615 Catherine is nowhere mentioned as patroness.
In 1615, the year parish priest Willem van Pede arrived, the name of Saint Catherine suddenly appears. The lady of the castle, Catharina Oudart, probably played a part; she and her husband Filips Happart were great benefactors of the church and good friends of the priests. There were also precedents: an old bell was called Catherine, Catharina vander Noot and Karel van Brecht had strongly supported the building of the new church, the north portal shows Catherine beside Cornelius, and there was already an altar of Saint Catherine.
The deans hesitated for a long time. In 1645 they crossed out Catherine again and wrote Cornelius; in 1661 it was Catherine once more. In 1674 a new high altar was dedicated to her, while the visitor acknowledged that Cornelius had been ‘until now the first patron’. From 1683 a middle way was chosen: Catherine as first and Cornelius as second patron. Two patron saints were in fashion at the time anyway, like St Michael and St Gudula in Brussels.
Cornelius remained the attraction
The people remained faithful to Cornelius, and after the deaths of the priest (1625), of Catharina Oudart (1629) and of Filips Happart (1631) he came to the fore again. New relics arrived in 1627, a new Cornelius altar in 1643, and on the spire of 1654 Cornelius is named before Catherine. He was also given a place on the pulpit (1687), on the choir panelling (1726) and on the organ case (1792). Nowhere in the village is there a chapel to Catherine; there is one to Cornelius.
The relics of Cornelius
In 1575 the church kept relics of Cornelius in a silver case, probably from Kornelimünster. According to tradition, on their arrival they stopped at a small stone chapel near the paper mills. Those first relics were lost. Parish priest Augustinus Beelden (1625-1639) obtained new ones through the Dominican Nicolaus Georgius, who declared that they came from the relic treasury of Utrecht. In 1627 the church had a silver mount made for the horn in which they are kept; this reliquary is still in use. Archbishop Boonen recognised the relics.
Shortly afterwards, in 1628, a small chapel with a statue of Cornelius was built at the corner of the Invalstraat and the St Cornelius road, where the L. Degreefstraat now meets the St.-Katarinastraat. It first stood on its own; when the street was widened in 1929-1930 it was built into the wall. In the early 20th century Mrs G. De Coninck set up a wayside altar there every year during the procession.
Catherine receives her relics
In 1665 the Carmelites of Brussels founded a confraternity of Saint Catherine in Diegem. Relics of Catherine, recognised in 1742 and given by canon Joannes Baptista Smet of St Martin's priory in Leuven, were solemnly brought in on 25 December 1749. Four priests carried the new shrine in procession from Haren to Diegem, with the guilds and a large crowd. After High Mass four Catherines of Diegem carried the relic three times around the church, and two other Catherines carried the candles. The shrine, made by Nicolaus Van Mons, cost 126 guilders.