fawkes assisted in filling the room with gunpowder, which was hidden beneath a wood store under the house of lords building, in a cellar leased from john whynniard. by march 1605, they had filled the undercroft underneath the house of lords with 36 barrels of gunpowder, hidden under a store of winter fuel. had all 36 barrels been successfully ignited, the explosion could easily have reduced many of the buildings in the old palace of westminster complex to rubble, and would have blown out windows in the surrounding area of about a one kilometre radius.