150 years of Big Ben

The Times reports: [edited]

When the great bell that bears the name Big Ben was first tested it cracked, and had to be broken up and recast.

Within a few months of being installed, the new bell cracked as well. The second time the damage was not too bad, and, since being patched up and turned a quarter-turn, the bell has given all but uninterrupted service.

Three times a week – on Monday, Wednesday and Friday – the clock is wound up by hand, a process that takes more than an hour because it is not possible to wind while it is chiming.

When it is going a bit fast or a bit slow (which it generally is) a mechanic places or removes a (pre-decimal) penny from the pendulum. Adding one speeds up the clock by two-fifths of a second a day.

Mr McCann, who rejoices in the title of 'Keeper of the Great Clock', gives a slightly embarrassed laugh when he is asked how he checks Big Ben. The answer is that he rings up the speaking clock. He does so from the phone in the clock room at five to the hour precisely, starting a stopwatch on the third pip, and then goes up the belfry to see when the hammer on Big Ben strikes the hour.

When the clock was commissioned as part of the rebuilding of the Palace of Westminster after the fire of 1834, the Office of Works called for, “a noble clock, indeed a king of clocks, the biggest the world has ever seen, within sight and sound of the throbbing heart of London”.

The Astronomer Royal also insisted on one that would be accurate to within a second, which was a tall order for such a huge [clock] which would be constantly exposed to the elements. Most clockmakers thought that it was impossible.

The man who proved otherwise was not even a professional clockmaker. Edmund Beckett Denison was a leading barrister and gifted amateur horologist who got himself involved in the selection of the final design, by the clockmaker Edward Dent.

Denison made many revisions to Dent’s original drawing, but his greatest contribution was to design a means of ensuring that the pendulum was separated from the movement of the hands, so that it was not affected by the weather. His ground-breaking invention, which is called a double three-legged gravity escapement, is the reason that Big Ben keeps such good time.

Denison made enemies wherever he went and, in the row over who was to blame for the cracked bell, fought and lost two libel actions. In one he was found to have befriended one of the technicians at the foundry that made the bell, got him drunk and bullied him into giving false testimony that the fault had been because of poor workmanship.

Big Ben is not immune to failure. Over the years it has been stopped by snow, mechanical failure and builders who have left paint pots where they shouldn’t; on one occasion it was slowed down by a flock of starlings settling on the minute hand.

- Big Ben weighs 13.5 tonnes (30,000lbs)

- The clock was first started on May 31, 1859.

- The BBC first broadcast the chimes on December 31, 1923

- The chimes are based on Handel’s Messiah, a phrase from the aria 'I Know that My Redeemer Liveth'. They were set to verse and the words inscribed on a plaque in the clock room, 'All through this hour Lord be my Guide That by Thy Power No foot shall slide'.

- When a bomb destroyed the Commons chamber in 1941, glass was blown out of the south dial but the clock kept going
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