Undercroft in the context of "John Grant (Gunpowder Plot)"

Guy Fawkes (/fɔːks/; 13 April 1570 – 31 January 1606), also known as Guido Fawkes while fighting for the Spanish, was a member of a group of provincial English Catholics involved in the failed Gunpowder Plot of 1605. He was born and educated in York; his father died when Fawkes was eight years old, after which his mother married a recusant Catholic.

Fawkes converted to Catholicism and left for mainland Europe, where he fought for Catholic Spain in the Eighty Years' War against Protestant Dutch reformers in the Low Countries. He travelled to Spain to seek support for a Catholic rebellion in England without success. He later met Thomas Wintour, with whom he returned to England. Wintour introduced him to Robert Catesby, who planned to assassinate King James I and restore a Catholic monarch to the throne. The plotters leased an undercroft beneath the House of Lords; Fawkes was placed in charge of the gunpowder that they stockpiled there. The authorities were prompted by an anonymous letter to search Westminster Palace during the early hours of 5 November, and they found Fawkes guarding the explosives. He was questioned and tortured over the next few days and confessed to wanting to blow up the House of Lords.

John Wright (January 1568 – 8 November 1605), and Christopher Wright (1570? – 8 November 1605), were brothers and members of the group of provincial English Catholics who planned the failed Gunpowder Plot of 1605, a conspiracy to assassinate King James I by blowing up the House of Lords. Their sister married another plotter, Thomas Percy. Educated at the same school in York, the Wrights had early links with Guy Fawkes, the man left in charge of the explosives stored in the undercroft beneath the House of Lords. As known recusants the brothers were on several occasions arrested for reasons of national security. Both were also members of the Earl of Essex's rebellion of 1601.

John was one of the first men to join the conspiracy, which was led by Robert Catesby. Christopher joined in March 1605. At about midnight on 4 November Fawkes was discovered and arrested, following which John, Christopher and the rest of the conspirators travelled across the Midlands, attempting to gain support for a popular uprising. Eventually the group opted to wait for the authorities at Holbeche House, on the border of Staffordshire. On 8 November the Sheriff of Worcester arrived with a large group of armed men, and both brothers were killed in the ensuing firefight.

Thomas Percy (c. 1560 – 8 November 1605) was a member of the group of provincial English Catholics who planned the failed Gunpowder Plot of 1605. He was a tall, physically impressive man; little is known of his early life beyond his matriculation in 1579 at the University of Cambridge, and his marriage in 1591 to Martha Wright. In 1596 his second cousin once removed, Henry Percy, 9th Earl of Northumberland, appointed him constable of Alnwick Castle and made him responsible for the Percy family's northern estates. He served the earl in the Low Countries in about 1600–1601, and in the years before 1603 was his intermediary in a series of confidential communications with King James VI of Scotland.

Following James's accession to the English throne in 1603, Percy became disenchanted with the new king, who he supposed had reneged on his promises of toleration for English Catholics. His meeting in June 1603 with Robert Catesby, a religious zealot similarly unimpressed with the new royal Stuart dynasty, led the following year to his joining Catesby's conspiracy to kill the king and his ministers by blowing up the House of Lords with gunpowder. Percy helped fund the group and secured the leases to certain properties in London, one of which was the undercroft directly beneath the House of Lords, in which the gunpowder was finally placed. The conspirators also planned to instigate an uprising in the Midlands and to simultaneously kidnap James's daughter, Elizabeth. Percy was to remain in London and secure the capture of her brother, Henry.