For clock towers in general, see clock tower.

The Clock Tower of the Palace of Westminster in London is located at the northwestern end of the building. It is often colloquially referred to as "Big Ben", after the 13-ton bell that is its best-known feature.

The tower is sometimes referred to as St. Stephen's Tower, but this title is not used by staff of the Palace of Westminster. This name may have come from St. Stephen's Hall, the western wing of the Palace of Westminster, which is the entrance used by visitors wishing to view the proceedings of the Houses of Parliament, and British subjects wishing to lobby their MPs.

The tower was raised as a part of Charles Barry's design of a new palace, after the old Palace of Westminster was destroyed by fire on the night of October 16, 1834. The tower is designed in the Victorian Gothic style, and is about 96 meters high.

The tower consists of brickwork with stone cladding, that is 61 meters high. The brickwork supports a framed spire from cast iron. The 15x15 meters square raft of the tower is made of 3 meters thick concrete, 7 meters below ground level. The tower has an estimated weight of 8.6 kilotones. The four clock faces are 55 meters above ground.

The clock in the tower was once the biggest in the world. One of the specifications of the clock was that it has to strike the first blow for each hour with an accuracy of one second. The mechanism of the clock was completed in 1854, but the tower was not yet ready by then.

The name Big Ben was first applied to a 16 ton hour bell, cast in 1856. Again, the tower was not finished yet, and the bell was mounted in the New Palace Yard . The bell cracked, and its metal was used to recast another bell, weighting 13.5 tons, which is the one used till today. Along with four quarter bells, it was mounted in the tower in 1858.

The clock and the bells become fully operational on September 7, 1859. Yet, less than a month later, the hour bell got a crack after being struck by the same hammer that broke the first hour bell. Then, for two years, the bell was substituted by the largest of the quarter bells. The hour bell was rotated so that the hammer omits the crack, and the bell become operational again in 1862.

The mechanism of the clock and of the chimes was overhauled several times since then.

The tower is somewhat leaning. On the height of the clock faces, the tower is out of plumb towards the northwest by about 35 millimeters.

Related topics

• Little Ben - a miniature clock tower found at the other end of Victoria Street
• Westminster Quarters - the chimes of the of the Clock Tower

Official links

• Explore Parliament