[5] The tower was designed by Sir Charles Barry and Augustus Pugin in a Perpendicular Gothic Revival style and was completed in 1859.

It is elaborately decorated with stone carvings and features symbols related to the four nations of the United Kingdom and the Anglo-Welsh Tudor dynasty.

An inscribed trowel in the Parliamentary Archives records that Emily, sister of Peto's daughter-in-law, was given the honour of laying the first stone.

[15] It was Pugin's last design before his descent into mental illness and death in 1852, and Pugin himself wrote, at the time of Barry's last visit to him to collect the drawings: "I never worked so hard in my life for Mr Barry for tomorrow I render all my designs for finishing his bell tower and it is beautiful".

[18] It was constructed using bricks clad on the exterior with sand-coloured Anston limestone from South Yorkshire, topped by a spire covered in hundreds of cast iron rooftiles.

[17] Above the belfry and the Ayrton Light are 52 shields decorated with national emblems of the four countries of the UK: the red and white rose of England's Tudor dynasty, the thistle of Scotland, shamrock of Northern Ireland, and leek of Wales.

They also feature the pomegranate of Catherine of Aragon, first wife of the Tudor king Henry VIII; the portcullis, symbolising both Houses of Parliament;[20] and fleurs-de-lis, a legacy from when English monarchs claimed to rule France.

It was intended to draw cool, fresh air into the Palace of Westminster; in practice this did not work and the shaft was repurposed as a chimney, until around 1914.

[18] Owing to this soft ground, the tower leans slightly to the north-west by roughly 230 mm (9.1 in) over 55 m height, giving an inclination of approximately 1⁄240.

[24] In the 1990s, thousands of tons of concrete were pumped into the ground underneath the tower to stabilise it during construction of the Westminster section of the Jubilee line.

It was last used in 1880 when atheist Charles Bradlaugh, newly elected Member of Parliament for Northampton, was imprisoned by the Serjeant at Arms after he protested against swearing a religious oath of allegiance to Queen Victoria.

[35] Originally, the dials were backlit using gas lamps, at first only when Parliament was sitting, but they have routinely been illuminated from dusk until dawn since 1876.

At the base of each dial is the Latin inscription DOMINE SALVAM FAC REGINAM NOSTRAM VICTORIAM PRIMAM, which means "O Lord, keep safe our Queen Victoria the First".

[39] When completed, the dials and clock hands were Prussian blue, but were painted black in the 1930s to disguise the effects of air pollution.

[42] As the tower was not completed until 1859, Denison had time to experiment before its installation in April that year: instead of using a deadbeat escapement and remontoire as originally designed, he invented a double three-legged gravity escapement, which provides the best separation between pendulum and clock mechanism, thus mitigating the effects of rain, wind and snow on the dials.

[48] On 10 May 1941, a German bombing raid damaged two of the clock's dials and sections of the tower's stepped roof and destroyed the House of Commons chamber.

[76] Since the tower was not yet finished, the bell was mounted in New Palace Yard but, during testing, it cracked beyond repair and a replacement had to be made.

To make the repair, a square piece of metal was chipped out from the rim around the crack, and the bell given an eighth of a turn so the new hammer struck in a different place.

[4][79][80] However, it is very clear from statements in the press at the time that the name derives from the nickname of Sir Benjamin Hall who was a tall man.

[90][91] The notional words of the chime, again derived from Great St Mary's and in turn an allusion to Psalm 37:23–24, are: "All through this hour/Lord be my guide/And by Thy power/No foot shall slide".

When a television or film-maker wishes to indicate a generic location in the country, a popular way to do so is to show an image of the tower, often with a red double-decker bus or black cab in the foreground.

[106] The Big Ben chimes (known within ITN as "The Bongs") continue to be used during the headlines and all ITV News bulletins use a graphic based on the Westminster clock dial.

The sound of the chimes is sent live from a microphone permanently installed in the tower and connected by line to Broadcasting House.

[108] On 27 July 2012, starting at 8:12 a.m, Big Ben chimed 30 times, to welcome the Games of the 30th Olympiad, which officially began that day, to London.

[109] On 21 August 2017, Big Ben's chimes fell silent for four years to allow essential restoration work to be carried out on the tower.

The decision to silence the bells was made to protect the hearing of the workers on the tower, and drew much criticism from senior MPs and Prime Minister Theresa May.

[110] The striking and tolling of the bells for important occasions, such as New Year's Eve and Remembrance Sunday, was handled via an electric motor; and at least one of the four clock faces always remained visible during the restoration.

[111][112] In February 2020, the renovations revealed that the Elizabeth Tower had sustained greater damage than previously thought from the May 1941 bombing raid that destroyed the adjacent House of Commons.

Other costly discoveries included asbestos in the belfry, the "extensive" use of lead paint, broken glass on the clock dials, and serious deterioration to the tower's intricate stone carvings due to air pollution.

[111][113] The 2,567 cast-iron roof tiles were removed and refurbished, and a lift was installed to make access easier, along with a basic toilet facility with running water, for the first time in the tower itself.