Big Ben's clock is fine-tuned with a small stack of old pennies
Resting on the pendulum of the Great Clock of Westminster sit pre-decimal pennies. Adding one nudges the centre of mass upward, shortening the pendulum's effective length so it swings a little faster, and each coin shifts the clock by 0.4 seconds a day. In 2009 three were swapped for an Olympic £5 coin.
Strictly, Big Ben is the bell, a 13.5-ton casting from the Whitechapel Bell Foundry named, it is said, after the tall Sir Benjamin Hall, who oversaw its installation. The tower was simply the Clock Tower until 2012, when Parliament renamed it the Elizabeth Tower for Queen Elizabeth II's Diamond Jubilee, matching the Victoria Tower at the palace's other end. Victorian journalists had their own name, St Stephen's Tower. Almost everyone still just says Big Ben.
It rose after fire destroyed most of the old palace in 1834. Charles Barry was the chief architect, but he asked Augustus Pugin to design the tower, Pugin's last work before mental illness and his death in 1852. Finished in 1859, it stands 316 feet high on concrete foundations 12 feet thick, sitting on gravel over soft London Clay. That ground makes it lean slightly north-west, helped along by 1990s tunnelling for the Jubilee line, though experts reckon it will not matter for another 4,000 to 10,000 years. A ventilation shaft by David Boswell Reid, dubbed the grandfather of air-conditioning, never worked as planned and served as a chimney instead.
The mechanism was a triumph. The lawyer and amateur horologist Edmund Beckett Denison designed it with the Astronomer Royal, George Airy, and while waiting for the tower he invented a double three-legged gravity escapement that isolates the pendulum from wind and snow on the hands. He never patented it, and it soon became standard for fine tower clocks. The clock is still wound by hand three times a week, about 1.5 hours each time, and it kept chiming through the Blitz even after a 1941 raid destroyed the Commons chamber.
Oddities abound. A lantern added in 1873 glows whenever the Commons sits after dark, originally so Queen Victoria could see it from Buckingham Palace. A prison room inside last held the atheist MP Charles Bradlaugh in 1880.
Source: Big Ben
