In 1605, a group of English Catholics led by Robert Catesby planned to blow up the House of Lords and kill King James I by hiding 36 barrels of gunpowder in the building's vaults. The plot was discovered after one of the conspirators sent a letter revealing the plan, and Guy Fawkes, who was guarding the gunpowder, was arrested. The plotters were tried and executed, and November 5th became a day of celebration in Britain commemorating the foiling of the Gunpowder Plot, known as Guy Fawkes Night.