To commemorate the 400th anniversary of the Gunpowder Plot, in the biggest historical and scientific experiment of its kind ever seen on television, Richard Hammond sets off on a quest to detonate a metric tonne of gunpowder beneath a full-sized reconstruction of the original House of Lords. On an old Cold War missile-testing site over a period of 2 months, building experts and engineers pour 650 tonnes of concrete into a steel framework to erect a ballistically accurate replica of the medieval building as it was when Guy Fawkes planned to blow it up.