What year did Big Ben suffer its first major breakdown?

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 usually extended to refer to both the clock and the clock tower as well. The tower is officially known as Elizabeth Tower, renamed to celebrate the Diamond Jubilee of Elizabeth II in 2012; previously, it was known simply as the Clock Tower. The tower had its 150th anniversary on 31 May 2009.

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.

Over the years, the clock's bells have been temporarily silenced and the clock was not illuminated because of air raids or to show respect to heads of states when they passed. A flock of starlings stalled the minute hand by just over 4 minutes in 1949, and in 1955 the clock was frozen by a blizzard.

On August 5, 1976 the clock suffered its first and only major breakdown. The air brake speed regulator of the chiming mechanism broke from torsional fatigue after more than 100 years of use, causing the fully wound 4-ton weight to spin the winding drum out of the movement, causing much damage. The Great Clock was shut down for a total of 26 days over nine months – it was reactivated on 9 May 1977.