The Great Westminster Clock overlooks the Palace of Westminster in London. Built by Edward Dent, the clock has been fully operational since 1859 and the clock tower is often mistakenly named Big Ben, which is in fact the name of the clock’s hour bell.


The clock mechanism sits in a room underneath the bell and is maintained by a team of three men.


The Great Clock will celebrate its 150th anniversary in 2009 and on 11 August 2007 the ‘bongs’ of Big Ben will be heard for the last time until September as maintenance work is carried out on the mechanism.



The pendulum is 3.9m long, weighs 300kg and beats every two seconds. Balanced on it are a number of pre-decimal pennies which help it keep time. Adding one penny would cause the clock to gain




Big Ben is the name of the bell used to strike the hour and weighs 13.5 metric tons. The first blow indicates the correct time and is joined by four quarter bells that weigh between one and four tons.



The hammer which strikes the bell weighs 200kg. The first bell was cast in 1856 but a crack soon appeared and a new one was cast.


The four 7m-wide clock faces each contain 312 separate pieces of opal glass.


Each face is illuminated with 28 energy efficient light bulbs that have a life of around 66,000 hours.



The clock tower is 96m high with 292 steps from ground level to the Clock Room and a further 101 steps to the lantern atop the tower.



Photos and text by Phil Coomes

Thats One Big Clock And 150 Years Old