The clock tower of the Houses of Parliament is known around the world as ‘Big Ben’. But that’s really just the nickname of the Great Bell inside the tower, which chimes on each hour. Officially the tower is named the Elizabeth Tower. It was originally St. Stephen’s Tower but was given its current name in 2012 to mark the Diamond Jubilee of Queen Elizabeth II. The tower contains five bells, of which the 13.7 tonne Great Bell – or Big Ben – is the largest. It was cast in the 1850s and takes its nickname from Sir Benjamin Hall who oversaw its installation. The clocktower includes a prison but it was last used in 1880 to hold a Member of Parliament who refused to swear allegiance to Queen Victoria.