tower clock, famous for its accuracy and for its massive bell (weighing more than 13 tons 【about 11,800 kg】). Strictly speaking, the name refers to only the great hour bell, but it is commonly associated with the whole Clock Tower, at the northern end of the Houses of Parliament (Parliament, Houses of), in the London borough of Westminster (Westminster, City of). The hands of the clock are 9 and 14 feet (2.7 and 4.3 metres) long respectively, and the clock tower rises to 316 feet (96 metres). Originally in coordination with the Royal Greenwich Observatory, the chimes of Big Ben have been broadcast, with a few interruptions, since 1924 as a daily time signal by the British Broadcasting Corporation (BBC).

The clock was designed by Edmund Beckett Denison (later Lord Grimthorpe (Grimthorpe, Edmund Beckett, 1st Baron)), partially built by Edward Dent (Dent, Edward John), and finished by his son, Frederick Dent. The clock and bell were installed together in 1859. The nickname is said by some historians to stand for Sir Benjamin Hall, the commissioner of works.

The first casting of the bell had failed; the second casting was made by George Mears of Whitechapel and was pulled to the tower by a wagon team of 16 horses. Shortly after it was installed, it too developed a crack and was kept out of service until its repair in 1862. In 1934 and 1956 the bell was restored and repaired. Maintenance work was performed on the clock in 2007.