He was born on 9 January 1695 in Elwick, County Durham to Thomas Ashmall[5] and Mary Addison. He was admitted to Lisbon College on 9 August 1711, at age 15, to prepare for the priesthood.[2][6] He was ordained on 18 February 1720 as a Roman Catholic priest in Portugal. He returned to England in 1723 where he became the chaplain to Mary Salvin at Elvet, County Durham until her death in 1727. He then moved back to his family estate in Amerston. He later moved to New House, County Durham where he remained as the priest until his death.[2]
^He is not to be confused with his uncle, for whom he is named after. It is known that his uncle's name was not used as a necronym in this case, as his uncle died in 1712, when Ashmall was 17.