On May 4, 1535, St. John Houghton, a Carthusian hermit, was hung and then quartered -- i.e., his body chopped up to be displayed -- at Tyburn, England. Required to take an oath in the wake of the Act of Succession, Houghton, who was prior of his community, had asked to be exempted, for which he had been imprisoned. However, after some difficult discussion, the community had concluded reluctantly that the oath could be taken, and Houghton was released. But when the Church of England broke ties with Rome through the Act of Supremacy, a new oath was required, and one that they could not in good conscience take, since doing so would be participating in schism. Houghton and several others again requested an exemption. They were arrested by Cromwell and put on trial for treason, and of course condemned to death.
Houghton was the first to die that day. According to the stories, he was not actually killed by the hanging, and so was still barely alive when they started taking out his heart. Houghton's death would be just the first of many over the next several years, so May 4 is a day for remembering all of the Martyrs of Tyburn.
In iconography Houghton is usually depicted as having a noose in one hand and his heart in another; sometimes he is giving his heart to Christ. He was beatified in 1886 and canonized in 1970.