From the Jesuits in Singapore website:
St. Thomas Garnet was born in 1574 at Southwark, England as the son of an Oxford don. Because Catholic colleges had been turned over to aggressive Protestants, young Thomas went to the continent in 1593 to attend the newly opened Jesuit college at Saint Omer.
Garnet's father Richard Garnet was at Balliol College at Oxford when restrictions were being placed on any students who seemed to be leaning toward Catholicism. The Catholic Encyclopedia praises him: "and by his constancy gave great edification to the generation of Oxford men which was to produce Campion, Persons and so many other champions of Catholicism." That generation of the Garnet family produced at least four religious vocations: Henry Garnet became a Jesuit and three girls, Margaret, Eleanor, and Anne braved exile to become nuns of the Augustinian convent in Louvain.
A storm in the English Channel caused Thomas and his companions to be captured by the English Navy who tried to force them to accept Elizabeth's religion. After months of abuse, they escaped. Later Thomas returned to England as a Jesuit.
His uncle, Fr. Henry Garnet, was superior of all Jesuits in England, and in charge of the entire network of priests working secretly among the Catholics who had refused to take the oath of Supremacy. Thomas Garnet worked near Warwickshire for six years, but his ministry ended with the discovery of the Gunpowder Plot. The Jesuit martyrs of this time were known for their intelligence, joy, humor, and for their deep understanding of martyrdom as apostolic.
On the scaffold he announced that he was the happiest man alive that day. His steadfastness in facing death impressed the crowds, so he was dead after hanging from Tyburn Tree before quartering and beheading. St. Thomas Garnet's missionary career during James I's reign shows the relative leniency of that king.
Because James wanted to preserve peace with Spain and France, Catholic countries he did not consistently target priests--and certainly not laity--for execution throughout his reign. Of course not every priest arrested during the reign of Elizabeth I was executed since some were held in Wisbech prison. Even after the terror of the Gunpowder Plot, Father Thomas Garnet, since nothing connected him then with any of the plotters, was (after torture) released into exile.