“There is no reason,” said Mike McCann, the man in charge of Big Ben, as he made his way down the 334 steps from the belfry at the top of the tower, “why it should not last forever.” As the world’s most famous timepiece celebrates its 150th anniversary, that is a forthright statement of faith in a masterpiece of Victorian engineering that was deemed so ambitious at the time of its inception that many clockmakers thought it could never be built.

That the Great Westminster Clock was completed was a triumph of perseverance and ingenuity over ill-fortune and acrimony. Not only was the building of Big Ben characterised by bitter rows between some of the key figures – the lawsuits stretched on for some time afterwards – but also when the great bell that actually bears the name Big Ben was 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, however, and, since being patched up and turned a quarter-turn, the bell behind the “bongs” – was ever a musical note so instantly recognisable? – has given all but uninterrupted service.

From today Big Ben – tourist landmark, London icon, symbol of parliamentary democracy – begins a year of anniversary celebrations starting with the launch of a website (www.parliament.uk/bigben). It is a very 21st-century way of marking the survival of an institution that is rooted in the technology of another era.

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. And when it is going a bit fast or a bit slow (which it generally is, that being the nature of mechanical systems) a mechanic places or removes a penny from the pendulum: an old, predecimal penny, of course; 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 does what everyone else does: 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. Simple, if not technologically sophisticated.

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 all very well for a small indoor clock, but a tall order for such a huge one, 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 was not, however, a man to waste his energy on considering the feelings of others. He 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.

Accurate Big Ben may be, but it 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.

It is, however, still going strong, and shows no sign of doing otherwise. “It is a privilege to look after it,” said Mr McCann. “We live in a throwaway society, and this is something that is going to be there for hundreds of years.”

The clock bombs failed to stop

— The bell – or Great Bell, nicknamed Big Ben – weighs 13.5 tonnes (30,000lbs)

— The clock was first started on May 31, 1859. Big Ben first struck the hour on July 11 that year

— 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

Source: Big Ben by Peter MacDonald

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