In the mid-17th century disaster struck. In 1665, the Great Plague of London killed 238 parishioners in a single week, and in 1666, the following year, the church was completely destroyed during the Great Fire of London, which burned much of the city. After the fire, the old church was replaced by an entirely new building designed by Sir Christopher Wren, one of his largest and most expensive works, taking seven years to build.