1890) had been designed by an architect called William Williams but his plan was then revised by Thomas Hardwick. The largest prison in Europe, it consisted of a hexagonal central courtyard with an elongated pentagonal courtyard on each outer wall of the central courtyard; the three outer corners of the pentagonal courtyards each had a tower one storey higher than the three floors of the rest of the building. Work had started under Hardwick in late 1812, but when the boundary wall it reached a height of about six feet high it began to tilt and crack.