Although the name ‘Big Ben’ is often used to describe Westminster’s clock tower, it is actually called the Elizabeth Tower. While the bell is officially called the Great Bell of Westminster, it’s generally referred to as Big Ben – a nickname of uncertain origin now known all over the world.
The Elizabeth Tower was designed by the architect Augustus Pugin and completed in 1859; it contains 11 floors and there are 334 steps to the belfry. The belfry houses the Great Clock of Westminster, built by Edward John Dent and his sons. Striking the hour to within a second of the time, the Great Clock has remained reliable since it entered service in 1859.
The time is shown on four dials, each seven metres (23 feet) in diameter, which are made of opalescent milk glass and can be lit from behind at night. The hour hand is 2.7 metres (8.9 feet) long, while the minute hand measures 4.2 metres (13.7 feet). The Great Clock started ticking on 31 May 1859, with the Great Bell’s strikes heard for the first time on 11 July the same year.
The Great Bell weighs 13.7 tons, is 2.2 metres (7.2 feet) in height and produces the note ‘E’ when tolled. Big Ben is fixed and struck by hammers from outside rather than swinging and being struck from inside by clappers. There are four other bells in the belfry and, when rung together, they produce the ‘Westminster chimes’.