Inside Big Ben: Why the iconic bell needs to be silenced for four years

The huge bell known around the world as Big Ben has ceased its regular bongs for four years while renovation work is carried out. The sound of the 13.5 UK ton (15.1 US ton, 13.7 metric ton) bell chiming every hour to the note of E, has become associated with Britain around the globe.

The bongs will sound for events such as New Year's Eve celebrations but the length of the silence has caused consternation among British politicians. Some want the time scale for repairs tightened, and House of Commons officials say they will take another look at the schedule once Parliament returns next month from its summer break. Prime Minister Theresa May has said it "can't be right".

The silencing of the bell is needed to ensure the safety of workers. Adam Watrobski, principal architect at the Houses of Parliament, rejected claims that the great bell that survived German bombing raids was the victim of overcautious health and safety regulations. "It is quite simply that we can't have the bells working with those people adjacent to it. It simply isn't practical to do that," he said.

The Elizabeth Tower, which was completed in 1859, is showing its age. The masonry is chipped and crumbling, and the clock faces are disintegrating.

As part of the works, Big Ben and the smaller bells in the tower will be X-rayed on site to check for any tiny internal cracks. The hammers which have struck the 13.7 tonne bell every hour for most of the last 157 years will be locked and disconnected from the clock.

The clock will be completely dismantled for the first time in its 158-year history, and the cogs will be X-rayed for metal fatigue. Its four dials will also be cleaned and repaired, their glass panels and cast iron framework renewed and the hands removed and refurbished.

One working clock face will remain visible at all times, telling the time silently, and it will be powered by a modern electric motor until the original clockwork mechanism is reinstated.

"Big Ben falling silent is a significant milestone in this crucial conservation project. As Keeper of the Great Clock I have the great honour of ensuring this beautiful piece of Victorian engineering is in top condition on a daily basis," said Steve Jaggs, keeper of the Great Clock. "This essential programme of works will safeguard the clock on a long term basis, as well as protecting and preserving its home – the Elizabeth Tower."

Officially called the Elizabeth Tower, the 96-metre-tall clock tower that houses Big Ben is believed to be the most photographed building in the United Kingdom, and is often used in films to establish the location as being London. During the repair work, scaffolding will obscure parts of the tower, and the clock faces will be covered at times. Its lower sections are already covered in scaffolding.

Big Ben has been silenced for repairs before, most recently in 2007, but this stretch is by far the longest. Adam Watrobski, principal architect at the Houses of Parliament, said authorities are well aware of how much interest the bell and the tower generate. "But you know at the end of the day all buildings have to be serviced," he said. Watrobski added that once this round of work is finished, "the building will be sound and secure for the next 60 years or so."