London's Big Ben traditionally chimes 12 times at midnight on New Year's Eve.
“Big Ben” properly refers to the Great Bell inside the Elizabeth Tower at the Palace of Westminster, although the name is often used for the entire clock tower. Its familiar hour strike sounds the arrival of the new year, and the broadcast chimes have become a major part of Britain's national countdown.
The tower's clock began operating in 1859. Big Ben's main bell strikes the hours, while four smaller quarter bells sound the quarter hours. At midnight, the hour sequence consists of twelve strikes, matching the twelve-hour face and the hour being announced.
The New Year's broadcast is associated with fireworks over the River Thames and celebrations around central London. Big Ben was silent for extended periods during conservation work beginning in 2017, though special arrangements allowed it to sound for important occasions, including New Year celebrations. The clock tower was officially renamed Elizabeth Tower in 2012.