The Clock Tower you see today is not the first tower to be built in Parliament's grounds.
The original tower was built in 1288-90 during the reign of King Edward I. It was located on the north side of New Palace Yard and contained a bell and clock. The bell, first named 'Great Edward' and later known as 'Great Tom', struck on the hour.
A second tower replaced the original in 1367. This was the first public chiming clock in England. By 1707, this tower had fallen into disrepair and was demolished. A sundial was put up in its place.
A terrible fire destroyed most of the Palace of Westminster in 1834. Architects were invited to submit their designs for the new Palace and a commission was set up to select the best. Out of 97 designs submitted, the architect Sir Charles Barry's was successful. However, his winning design did not feature a clock tower. He added this to his design in 1836.
Construction of the Clock Tower began in September 1843. This is the iconic tower which stands today in the Houses of Parliament.