LONDON, May 31 (Xinhua) -- Big Ben's Great Clock, the world's most iconic timepiece, turned 160 Friday as vital conservation work continues to ensure its future.
The clock, towering above the Houses of Parliament, has become one of the most photographed attractions in London.
It was installed in the Elizabeth Tower in 1859 featuring a revolutionary double three-legged gravity escapement, ensuring its accuracy by making sure the pendulum was unaffected by external factors, such as wind pressure on the clock's hands.
The clock was installed in April 1859 and at first it wouldn't work as the cast-iron hands were too heavy. Once they were replaced by lighter copper hands, it successfully began keeping time on May 31, 1859.
The Parliament's team of expert clock mechanics have taken the Great Clock apart piece by piece to undertake its biggest ever overhaul of all the components, as restoration continues on the Elizabeth Tower.
Thousands of components weighing over 11 tonnes were winched down from the tower before work could begin.
An electric motor has been temporarily installed to drive the hands of the clock while the mechanism is restored.
When the essential work to conserve the Elizabeth Tower is completed, the clock parts will start making the journey back up the tower to be reassembled, and the mechanism will be reattached to the hands and the bells.
"After 160 years of near continuous use the clock mechanism is in remarkably good condition. It has been well looked after over the years, but now we are cleaning, inspecting, painting and testing every single cog and wheel to ensure it can continue keeping time for the nation for another 160 years and beyond," said Parliament Clock Maker Ian Westworth.
The story of the clock goes back even further to 1846 when Astronomer Royal Sir George Airy headed a competition to design and build the clock. Airy wanted to see the most accurate turret clock in the world, and stipulated it must be accurate to within one second.