Cuthbert Mayne, raised and ordained in the Church of England, had been befriended while at the University of Oxford by Edmund Campion and Gregory Martin.

Under their influence, Mayne also had converted to Roman Catholicism.

Like them, he had fled to the European continent; had been ordained a Roman Catholic priest at the English College at Douai, France; and returned in 1576 as a missionary to Cornwall.

He disguises himself as the steward of a local landowner but is discovered and put to death at Launceston on November 30, 1577, on charges of denying the queen's spiritual supremacy, saying Mass, and possessing an Agnus Dei (a type of Roman Catholic devotional medallion).

Mayne is the first of the Douai-trained priests to be martyred.