Blessed Margaret Pole, beatified in 1886 by Pope Leo XIII with 53 other martyrs, was beheaded on May 27, 1541. EWTN posts this biography from Father Alban Butler:
The life of Margaret Pole, Countess of Salisbury, was tragic from her cradle to her grave.l Nay, even before she was born, death in its most violent or dreaded forms had been long busy with her family—hastening to extinction a line that had swayed the destinies of England for nearly four centuries and a half. Her grandfather was that splendid Richard Neville, Earl of Warwick, the mighty King-maker, who as the "last of the Barons," so fittingly died on the stricken field of garnet, and whose soldier's passing gave to Shakespeare a theme worthy of some of his most affecting lines. Her father was the George, Duke of Clarence, brother of Edward IV, whose death in the Tower in January, 1478, has been attributed to so many causes. The murdered "Princes in the Tower," Edward V and his little brother, the Duke of York, were her first cousins, while her only brother, Edward, Earl of Warwick, was judicially murdered by Henry VII to ensure his own possession of the Crown. The list of tragedies in the family of the Blessed Margaret is still far from complete, but sufficient instances have been given to justify the description we have given of her whole career. . . .
The Countess of Salisbury was taken to East Smithfield early in the morning of 28th May, 1541, and there beheaded on a low block or log in the presence of the Lord Mayor, Aldermen, and a few other spectators. The regular headsman was away from London at the time, and his deputy, an unskilful lout, hacked at the blessed Martyr in such a way as to give some foundation to the story afterwards made current by Lord Herbert of Cherbury, that she had refused to lay her head on the block and was, therefore, struck repeatedly by the executioner till she fell dead. Before her death, she prayed for the King, Queen (Catherine Howard), Prince of Wales (later Edward VI), and the Princess Mary Her last words were: "Blessed are they who suffer persecution for justice' sake for theirs is the Kingdom of Heaven."
The body of the Blessed Margaret, Countess of Salisbury, was interred in the Tower, in that Chapel dedicated to St. Peter's Chains, whose illustrious dead and historic associations are enshrined in Macaulay's memorable lines. She was declared Blessed with many of the rest of the English Martyrs by Leo XIII, 29th December, 1886. Others than her co-religionists, no doubt, like to reflect that a life, so marked by piety, and so full of griefs ever heroically borne, has after the lapse of nearly four centuries been thus honoured, and that the last direct descendant of the Plantagenet line has her place in the Hagiography of the Church so long associated with their sway.
This parish has a beautiful icon of Blessed Margaret Pole, holding up the white gown of a martyr with the banner of the Five Wounds of Christ on its front. While she had escaped the Exeter conspiracy with her life--although imprisoned in the Tower--when Thomas Cromwell's agents found the emblem of the Five Wounds among her possessions they determined that she was supportive of the rebels who opposed the Dissolution of the Monasteries and other religious changes.
"Macaulay's memorable lines" about St. Peter ad Vincula are from The History of England from the Accession of James II:
In truth there is no sadder spot on the earth than that little cemetery. Death is there associated, not, as in Westminster Abbey and Saint Paul's, with genius and virtue, with public veneration and with imperishable renown; not, as in our humblest churches and churchyards, with everything that is most endearing in social and domestic charities; but with whatever is darkest in human nature and in human destiny, with the savage triumph of implacable enemies, with the inconstancy, the ingratitude, the cowardice of friends, with all the miseries of fallen greatness and of blighted fame. Thither have been carried, through successive ages, by the rude hands of gaolers, without one mourner following, the bleeding relics of men who had been the captains of armies, the leaders of parties, the oracles of senates, and the ornaments of courts.