Big Ben is the nickname for the great bell of the clock at the north end of the Palace of Westminster in London,and is generally extended to refer to the clock or the clock tower as well.
Some believe this extension to be incorrect, but its usage is now entirely commonplace. It is the largest four-faced chiming clock and the third-tallest free-standing clock tower in the world.It celebrated its 150th anniversary in May 2009, during which celebratory events took place.The clock first ticked on 31 May 1859. The clock's movement is famous for its reliability. The designers were the lawyer and amateur horologist Edmund Beckett Denison, and George Airy, the Astronomer Royal. Construction was entrusted to clockmaker Edward John Dent; after his death in 1853 his stepson Frederick Dent completed the work, in 1854.
The nickname Big Ben is the subject of some debate. The nickname was applied first to the Great Bell; it may have been named after Sir Benjamin Hall, who oversaw the installation of the Great Bell, or after boxing's English Heavyweight Champion Benjamin Caunt.Now Big Ben is sometimes used, strictly-speaking incorrectly, to refer to the clock, the tower and the bell collectively, although the nickname is not universally accepted as referring to the clock and tower.Some authors of works about the tower, clock and bell sidestep the issue by using the words Big Ben first in the title, then going on to clarify that the subject of the book is the clock and tower as well as the bell.