Agnes was poor and illiterate. She was born in Cornwall and worked in Exeter as a domestic servant for a while. Whilst in Exeter she heard things that changed her life. There is some evidence that she was actually present in the crowd when Benet was martyred for the Faith. 'Upon the Sundays I visited the Sermons, and there have I learned such things as are so fixed in my breast that death should not separate them.'
Leaving Exeter she returned to Cornwall and married a man called Prest, who turned out to be an ardent Papist. They had numerous children, whom Prest brought up to believe the things he did. They 'were much addicted to the superstitious sect of Popery'. She was a simple Bible-believing woman, he was an ardent Papist; it was not a good match. 'When I would have him to leave idolatry and to worship God in Heaven, he would not hear me, but he with his children rebuked and troubled me.' Prest tried to compel his wife to go to Mass, make her Confession and follow the Cross in procession, but Agnes refused to do any of these things. The persecution became so great that finally she fled.
Love of home and family proved so strong that Agnes returned, only to be met with a heartless reception as her husband and some neighbours took her to the Parish Priest and accused her of Heresy. She was arrested and kept in gaol at Launceston for some three months, and then transferred to Exeter. The charge was, 'Heresy chiefly against the Sacrament of the Altar and for speaking against Idols'.
Bishop Turberville said she ought to be burned for this heresy, to which she said that she would 'rather die than worship that foul idol which with your Mass you make a god ... to be worshipped of all men'. Agnes Prest tried to show Turberville that worshipping a piece of bread as God was both absurd and blasphemous, but being a devout follower of the Pope he would have none of it.
She insisted that the Body of Christ remained in Heaven until He came again (as the Apostles' Creed declares) but the Bishop said that any priest could bring down Christ and turn the bread into His Body.
She was ordered to give up her religion, or be burned as a heretic. Sentenced to death, she was offered one last chance to turn from her faith, but again she refused.
On 15th August 1557, this 54-year-old woman was led outside the city walls to Southernhay where she was burned to death. Her crime? She would not bow down and worship a piece of bread.