When Henry VIII issued his “Act of Supremacy” declaring that all who refused to take an oath recognizing him as head of the Church of England committed an act of high treason, the Carthusian Monastery of London (now the Charterhouse) refused and were sentenced to death.
The first to die were the Carthusian Prior of London, John Houghton, and two of his brothers, Robert Lawrence and Augustine Webster, who were hanged, drawn and quartered, on May 4, 1535. The Prior is said to have declared his fidelity to the Catholic Church and forgiven his executioners before dying. These Carthusians were the first martyrs to die under the reign of Henry VIII.
Two more Cathusians were killed on June 19 of that year and by August 4, 1540, all eighteen monks had been tortured and killed for refusing to place their allegiance to the king before their allegiance to the Pope.
Painting: Andrew Benjamin Donaldson (1840–1919) Carthusian martyrs at Tyburn on 4 May 1535