Mary Heywood was born in Swinton, near Manchester, into a wealthy and cultured family. Her father was a banker and a scholarly man. Her mother's family owned land in two counties. Mary grew up in the beautiful surroundings of Hope End, in Herefordshire. Educated at 1828:home she spoke three foreign languages and became a very accomplished singer. Yet what she valued most when she reminisced about her family home was its Christian atmosphere. 

1848: Coming from such a home it is not perhaps surprising that George Sumner, the youngest son of Charles Sumner, Bishop of Winchester, fell in love with her when they met in Rome where she was completing her musical education. Married at St James, Colwall, they embarked on 61 years of married life.

For nearly thirty years Mary was fully occupied in bringing up their three children and supporting her husband's ministry, in the parish of Old Alresford near Winchester, by providing music and teaching Bible classes.

1876: Mary decided that a new organisation was needed in the parish and the first branch of Mothers' Union was begun. She was spurred into action when her eldest daughter gave birth to her first baby. Mary remembered her feelings of inadequacy as a young mother charged with the terrible responsibility for a new life. She believed that women from every class needed to understand that motherhood was a profession and be equipped to perform it. Motherhood involved more than providing for the physical needs of children. The primary responsibility of mothers was to raise their children in the love of God. Mothers could only do this, she believed, if their lives were firmly rooted in prayer. 

Her plan for a new form of mothers meeting, bringing together mothers of all classes, did not start auspiciously. Having gathered the women of the parish in the Rectory, Mary could not present her ideas due to nerves. She had to call them together again a week later to explain the objects of the new society and to give out simple cards containing practical suggestions.

1885: Perhaps little more would have been heard of this organisation but for Bishop Ernest Wilberforce of Newcastle. Feeling suddenly that he had little of relevance to say to a women's meeting made up of 1000 poor and anxious women at the Portsmouth Church Congress, he called on Mary to speak. Despite her initial resistance, as at that time respectable women did not address public meetings, she agreed. Painting a picture of the low moral standards in the country, she asked what could be done to improve the national character. Her answer was that the power for change lay in the hands of mothers. If women united in prayer and committed themselves to a Christian life the nation could be transformed.

The meeting responded to her passion and conviction with a rousing ovation. It was on this wave of public enthusiasm that the Bishop of Winchester decided to make Mothers' Union a diocesan organisation. This decision was destined to change the lives of many far beyond the boundaries of the diocese of Winchester.

1921: On August 9, 1921 Mary died at the age of 92. She is buried with her husband, who had died twelve years before, in the grounds of Winchester Cathedral. She is commemorated in the liturgical calendars of the Church of England, Church in Wales and other provinces on the date of her death.