In 1605, a group of Catholic conspirators plotted to assassinate King James I of England (and VI of Scotland) by blowing up the House of Lords during the opening of parliament.
They hid kegs full of gunpowder in the cellars beneath the chamber where the king and the rest of the political elite would assemble. Enough powder was stored to completely destroy the building and kill everyone present.
One of the conspirators, Guy Fawkes, was tasked with igniting this huge bomb. It is Fawkes’ effigy that is still burned on 5 November bonfires to this day. (From http://www.bbc.co.uk/history/british/civil_war_revolution/launch_gms_gunpowder_plot.shtml)