The dedication of the parish to the Immaculate Conception of the Blessed Virgin Mary pre-dates the founding of the parish itself and can be traced back to the exiled French Olivetan nuns who had sought refuge in Bicester during the early years of the twentieth century. They were the successors to a community of Nuns of the Immaculate Conception that had been founded by Mademoiselle le Chevalier in 1825. They set up home in Bicester on the 7th of December 1904, the eve of the Solemnity of the Immaculate Conception of the Blessed Virgin Mary. The chapel in their convent, which they shared with Bicester’s Catholic community, was dedicated to the Immaculate Conception and when they left in the 1920s Bicester’s Catholics continued to use it as their place of worship until the opening of the present church in March 1963. Devotion to Mary can be traced back to the early church, possibly as early as the late third century and were given a boost in the fourth century when, in response to the Arian heresy, the Church affirmed its teaching that the Blessed Virgin Mary was indeed the Mother of God. Libraries of books can be and have been written about devotion to Our Lady. The Church, through its liturgy and other prayers rightly honours Mary as the first and most perfectly redeemed of humanity.
Marian devotions take place each Saturday evening at 5.30 and consist of recitation of the rosary, the Litany of Loreto and, just before the start of the Vigil Mass, the Angelus, or, in Eastertide, the Regina Caeli. In addition, the rosary is also recited in the Blessed Sacrament Chapel following the daytime weekday Masses. During the recitation of the Angelus, it is customary to ring a bell eighteen times – traditionally the age of Our Lady at the Annunciation.