Upon the accession of
Mary I in 1553, Harpsfield returned to England, took the degree of DCL at Oxford in 1554, and became
Archdeacon of Canterbury in the same year, serving under
Reginald Pole. He superintended hundreds of trials targeting lay Protestants in London, which resulted in punishments and intimidation (though not any charges under the
revived Heresy Acts). He played an active role in the administration of the diocese of Canterbury, where he zealously promoted heresy trials. ''
Foxe's Book of Martyrs'' (1563 edition) identifies him as "the sorest and of leaste compassion" among the archdeacons involved in the
Marian Persecutions and holds him responsible for many deaths in the diocese. ==Imprisonment and death==