What if the Gunpowder Plot had succeeded? In 2005 a team built a full-size replica of the Parliament building which they destroyed with 1,000kg of gunpowder (the plotters had likely stored around 2,500kg). They concluded no one within 100m of the blast could have survived

The Gunpowder Plot of 1605, in earlier centuries often called the Gunpowder Treason Plot or the Jesuit Treason, was a failed assassination attempt against King James I by a group of provincial English Catholics led by Robert Catesby who sought to restore the Catholic monarchy from the Church of England after decades of intolerance against Catholics.

The plan was to blow up the House of Lords during the State Opening of Parliament on 5 November 1605,[a] as the prelude to a popular revolt in the Midlands during which James's nine-year-old daughter, Elizabeth, was to be installed as the Catholic head of state. Catesby may have embarked on the scheme after hopes of securing greater religious tolerance under King James had faded, leaving many English Catholics disappointed. His fellow plotters were John and Christopher Wright, Robert and Thomas Wintour, Thomas Percy, Guy Fawkes, Robert Keyes, Thomas Bates, John Grant, Ambrose Rookwood, Sir Everard Digby and Francis Tresham. Fawkes, who had 10 years of military experience fighting in the Spanish Netherlands in the failed suppression of the Dutch Revolt, was given charge of the explosives.

Jacobean 9/11 Would have prompted merciless anti-Catholic pogroms; consolidated absolutist royalism in Britain; aborted stillborn the possibility of 1642, 1688, 1776 ... think of that when you see someone wearing one of those stupid Guy Fawkes masks as a badge of "resistance"