As the UK Parliament prepares to celebrate the 150th anniversary of its world-famous clock, E&T examines the history of Big Ben.
With a few seconds to go to midday, I am told to put my fingers firmly in my ears. Even then, when the four quarters are struck, the noise is phenomenal, but nothing compared to the striking of the hour bell, Big Ben. The belfry reverberates with the sound which they say could be heard all over London when the 300kg clapper was first triggered on 11 July 1859.
Nowadays, of course, amid the roar of London's traffic, it is not so noticeable away from the immediate vicinity of the Palace of Westminster, but for many people all around the world its instantly recognisable sound is familiar from the radio and television, especially on New Year's Eve.
Though over time the clock tower has become known as Big Ben, it is in fact only the hour bell that has that nickname. The mechanism for powering the hands on the four dials and operating the quarter bells and the hour bell is correctly known as the Great Clock of Westminster.
Showing me around the tower are Paul Roberson and Ian Westworth, who are responsible (together with Huw Smith) for the maintenance of the Great Clock and the other 2,000 clocks in the Palace of Westminster, of which 450 are mechanical or antique. Roberson has been an horologist all his life, taking an apprenticeship in watch and clockmaking straight from school. An obvious clock enthusiast, he says: "It gets under your skin. I am interested in anything mechanical." Westworth worked as a turret clock restorer before becoming a Place of Westminster clockmaker four years ago. Both are proud of the Great Clock as, Westworth says, "it still does exactly what it was designed to do 150 years ago".
After the destruction of both houses of parliament by fire in 1834, it was decided that the new buildings should have a grand tower housing "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".
In his specification, the Astronomer Royal, George Airy, wrote: "The striking machinery is to be so arranged that the first blow for each hour shall be accurate to the second of time." No clockmaker thought it remotely possible to construct a mechanism of the required size that, in addition to sounding five bells and powering hands of four dials, would keep such accurate time. But an appeal by the Worshipful Company of Clock-makers for a less onerous specification was turned down and three horologists were invited to tender.
Edmund Becket Denison
If Edmund Becket Denison had not been invited to join George Airy as a second referee, it is unlikely that such an accurate clock would have been built. Though a barrister by profession, Denison was a gifted amateur horologist, the author of articles and the designer of some fine clocks. He favoured the submission of EJ Dent & Company, to whom he suggested many improvements that amounted to a redesign, and it was to that firm that the contract was awarded in 1852.
Within three years the clock was complete, but neither the bells nor the tower in which it would be installed had been finished. However, the delay was fortuitous as it gave Denison the time to design a mechanism that would ensure the clock's accuracy.
The problem with turret clocks had always been how to prevent the external forces on the hands being reflected back to the pendulum thus affecting the clock's accuracy. This is achieved with an escapement, a device that transfers the power of the descending weight to the hands by hitting (impulsing) the pendulum. It was Denison who came up with the double three-legged gravity escapement, an ingenious yet simple device, which, as Roberson says, was "a massive advancement, without which the clock would not be here now". It was successfully tried out in the harshest of conditions in a clock built by Dent for Fredericton Cathedral in New Brunswick, Canada and thereafter became widely used in turret clocks.
While Denison carried out further trials, the great bell had been completed at a foundry in Stockton-on-Tees in northern England and was transported by water arriving in London on 21 October 1856.
Trial and error
With the clocktower still incomplete, it was set up on a specially built gallows near the foot of the tower, where for almost a year it was struck regularly until, on 17 October 1857, a 1.2m crack appeared. The only solution was to break it up and, in April 1858, a new, lighter, bell, which would become Big Ben, was cast at the Whitechapel Foundry in London's East End.
In the meantime, the tower designed by Charles Barry, with the decoration and beautiful dials by Augustus Pugin, was completed. In the summer of 1858, the bells were hand-winched up the shaft, the hoisting of Big Ben taking teams of men working in relays some days to complete.
With the installation of the operating mechanism below the Belfry, all was ready by spring 1859. However, each time the minute hands approached the hour, they stopped. The construction of lighter minute hands of hollow copper and hour hands of copper-backed hollow gunmetal allowed it to operate successfully.
As far as is known, the clock started officially on 31 May 1859, with Big Ben first sounding the hour on 11 July and the quarter bells chiming from 7 September. The public appreciated the sound but, perhaps predictably, the Members of Parliament complained that it was too loud.
The trouble with the clock hands had brought Denison to near despair, so it is not difficult to imagine how he felt when told, less than a month later, that a 30cm-long crack had appeared in Big Ben. There were recriminations all round: Denison accused the Whitechapel Foundry of poor workmanship while the foundry put the damage down to Denison's continued use of a 300kg hammer. Two ensuing libel actions both found in favour of the foundry over Denison.
To dismantle the clock, lower the bell and recast it was not considered possible. So, as the crack was neither as deep nor as long as that in the first bell, a slot was cut out to prevent it spreading, a 200kg hammer installed, and the bell turned through about 90°, where it has remained ever since without further problems.
Of course, there have inevitably been a few problems with the clock mechanism, but normally these are discovered and put right before they become severe. Though it has been given a thorough overhaul for its 150th anniversary, Roberson says: "There isn't a servicing schedule like a car. We are up here three times a week and can see any fault developing."
With the last chime of Big Ben, we remove our fingers from our ears, but the resonance seems to go on and on - "for 30 seconds", I am told by Roberson. From the belfry we make our way down to see the dials. Now each illuminated by 28 long-life bulbs of 85W, they were originally lit by gas jets and looked after by a gas man who was required to stay in the tower all night.
As we make our way down the remainder of the 334 steps, it is clear that this is more than just a job for those who work with Big Ben. As Westworth says: "Working on the Great Clock of Westminster is one of the things most horologists want to do because it is probably the most prestigious clock in the world." Roberson adds: "I have been involved in clocks all my life but this is the most famous clock in the world and we are the ones responsible for looking after it."