By the second century, however, Christian Copts in Egypt, familiar with the ancient mother-goddess Isis, refashioned Mary the humble woman into the magnificent Mother of God in which the human and the divine combined. When the Fathers of the Church met for the First Council, at Nicene in 325 AD, Mary's extraordinary character became part of the Creed Christians repeat to this day: hers was a virgin birth, with Jesus conceived of the Holy Spirit. (The Koran also emphasises the point that Maryam was a virgin. Ambrose, bishop of Milan, saw Mary, chaste and obedient, as a perfect role model for the men and women in religious orders who were becoming the backbone of the new faith.)

In Byzantium Mary was elevated to cult figure. A furious row over her status - was she wholly human, or, as God's mother, more than human - split the court and, spilled into the streets of Constantinople. In the end, Mary was recognised as Theotokos, the God's bearer. Emperor Theodosius II and his powerful sisters turned devotion to her into the defining characteristic of their dynasty. Pulcheria, the emperor's eldest sister, took a vow of virginity and travelled through the empire founding churches in Mary's name. She created a pattern repeated down the centuries by extraordinary abbesses, anchoresses, canonesses, nuns and beguines.

These women, all with varying links to religious orders, held up the image of the pious mother as a shield behind which they could dedicate themselves to scholarship, politics and the arts. Mary as patron of the first feminists sounds counter-intuitive - Marina Warner's brilliant 1976 study of Mary as Catholic icon, Alone of All her Sex, depicted Marian devotion as a beautiful but ultimately misogynist enterprise; but some of the most enthralling pages of Rubin's scholarly history quote from the works of magnificent women such as the musician, scientist and theologian Hildegard of Bingen and the mystic poet Julian of Norwich, and chronicle the little-known influence of the German canoness and poet Hrotsvitha and the French nun and writer Ida of Nivelles.