Van Mierlo was born in the City of
Helmond on 2 February 1518, then the
Duchy of Brabant, part of the
Habsburg Netherlands. He entered the
Dominican Order in 1533, at the age of 15, in
's-Hertogenbosch. He professed his
religious vows as a
friar of the Order the following year. After completing his studies, he was
ordained a
Catholic priest in 1542. He gained the degree of
doctor of theology and was appointed as the
Prior Provincial for Holland. Van Mierlo was named the Bishop of Haarlem and the Abbot of Egmond Abbey in March 1570 by
Pope Pius V. He was welcomed to that city in early 1571, where he was
consecrated a
bishop on February 11 of that year in the original
Cathedral of St. Bavo by
Franciscus van der Velde, the
Bishop of Antwerp. Van Mierlo had to re-sanctify the church in 1573. In
Veere, in 1577, Van Mierlo set his seal to the "
Satisfactie van Haarlem" wherein he promised to swear allegiance to
Willem the Silent rather than
Philip II of Spain, on the condition that the Catholics would keep the same rights as Protestants. This was reversed a year later on May 29, the
Feast of Corpus Christi that year, when Calvinist supporters again stormed the cathedral, this time during the celebration of the
Hour of
Terce at the 9th hour of the day, or 3:00 P.M., ravaging the altars, killing a priest and injuring several others. The
provost of the cathedral,
Jacobus Zaffius, who had witnessed the Amsterdam "
Alteratie" two days earlier, saw it happen. Van Mierlo fled to
Rome where
Pope Gregory XIII appointed him
coadjutor bishop of the
Diocese of Münster. He was then appointed Bishop of
Deventer in 1587, where he needed to re-sanctify the local churches. Van Mierlo died the year of his appointment at the age of 69, and was buried in the
Lebuïnuskerk of Deventer. After Van Mierlo fled Haarlem, the city was no longer an official Catholic
bishopric, and the period from then onwards until 1798 (during the French occupation) was known as the
Hollandse Zending, or Dutch Mission, where the Catholics had to worship in secret. However, the
Haarlemse kapittel or
cathedral chapter, remained active and St. Bavo was always called the
cathedral by townsfolk, even after the
Cathedral of Saint Bavo was built in the 19th century to serve the re-established Catholic diocese. ==References==