1840-2012: Big Ben and Elizabeth Tower

1840
Construction of the new Palace of Westminster began. Architect, Charles Barry won the commission to design the new palace and included a clock tower in his final designs.

1843
Construction began on the Clock Tower. Foundation stone was laid.

1846
A competition was held to decide who should build the clock. The Astronomer Royal, Sir George Airy was the referee. Stipulations for the clocks accuracy meant it took seven years before the designs were finalised.

1852
John Dent was appointed to build the clock to the designs of Edmund Beckett Denison. This was the same year that the new Palace of Westminster, designed by architect Sir Charles Barry with the assistance of Augustus Welby Pugin, was opened by Queen Victoria at the State Opening.

1854
The clock mechanism was completed.

1856
The first 'Big Ben' bell was cast at Warners of Norton near Stockton-on-Tees, the bell was originally to be called 'Royal Victoria'.

1857
The first 'Big Ben' developed a four foot (1.2m) crack during testing and was condemned. Warners, the bell's manufacturer, and Edmund Beckett Denison, designer of the Great Clock, clashed over who was responsible for the damage.

1858
In April, the second 'Big Ben' was cast by the Whitechapel Bell Foundry in East London. It was transported to New Palace Yard on a carriage drawn by 16 white horses and raised to the belfry.

1859
The Great Clock started ticking on 31 May and the Great Bell's strikes were heard for the first time on 11 July. Later that year, Big Ben was found to be fractured in two places. While a solution was sought, Big Ben remained silent with the largest quarter bell striking the hourly chime.

1863
At the suggestion of Sir George Airy, the Astronomer Royal, Big Ben was turned by an eighth and the hammer size was reduced thus allowing Big Ben to strike the hours once more. A telegraphic link to the Greenwich Observatory was installed to check the accuracy of the time keeping.

1923
BBC Radio first broadcast Big Ben's chimes to the United Kingdom on New Year's Eve.

1932
Big Ben's strikes broadcast internationally for the first time by the Empire Service (later the World Service) as part of King George V's Christmas broadcast.

1939
From this date until April 1945, the clock dials remained in darkness to comply with blackout regulations during the Second World War.

1945
The clock dials were re-illuminated when the wartime blackout regulations were lifted.

1976
In the middle of the night on the 5 August, a mechanical failure caused serious damage to the Great Clock. The pendulum weights spiralled out of control down the weight shaft and the clock mechanism exploded. Big Ben was silenced for nearly nine months. The repairs were completed in time for the bells to ring out to mark the occasion of Queen Elizabeth II's Silver Jubilee visit to Westminster Hall in May 1977.

2007
Big Ben and the quarter bells were silenced from 11 August to 1 October while the Great Clock underwent essential maintenance work.

2009
Big Ben celebrated its 150th anniversary with a year of events and activities.

2012
The Clock Tower was renamed the Elizabeth Tower to honour Queen Elizabeth's Diamond Jubilee.