Londoners were not happy to hear the news, and there was lament on Twitter, with many recalling how the hourly bongs of Big Ben serve as a kind of base note for their lives.

"A silent Big Ben will be super eerie," tweeted Rob, a history student at King's College. "I could hear the chimes from my room in Euston, they're the sound of London!"

"It will be very sad, but it needs to be done," said Kirsten Hurrell, 71, a news agent who runs a busy stall that faces the clock tower.

Hurrell said the gong of Big Ben might be one of those things in life you don't miss until they are gone. "Quite honestly, we live with it and half the time we don't hear it," she said. "But we will miss it when we will suddenly find it's not there anymore."

Tourism officials were glum but hoping for the best.

A selfie with the Great Clock atop Elizabeth Tower along the Thames River is almost mandatory. The Palace of Westminster, home to the houses of Parliament, is one of the top five visited sites in London, and Big Ben is the star of the show.

The tower will soon be fully swaddled in metal scaffolding and three of the four clock dials covered. The last gongs of Big Ben, before its long rest, rang out at noon Monday, August 21, London time. Large crowds witnessed the event. The repairs should be complete sometime in 2021, authorities promised.

"Big Ben has marked the hour with almost unbroken service for the past 157 years," said Steve Jaggs, keeper of the Great Clock, noting that the complex renovation - budgeted at about $US40 million - is designed to safeguard clock and tower for future generations.

"Big Ben falling silent is a significant milestone in this crucial conservation project," the clock keeper said.

The actual bell is not the problem. It is the clock that rings the bell that needs repairs.

Cast by the Whitechapel Bell Foundry, the 13-ton hour bell was the largest of its day, its first performance celebrated by Parliament in 1859.

In all these years, Big Ben bonged through good times and bad, including the Blitz, Germany's eight-month aerial bombardment of London during World War II.

The hour bell has been silenced for long periods a few times before. Just weeks into its service, Big Ben cracked. Apparently the striking hammer was too heavy. A lighter hammer was installed, the bell was turned, and Big Ben was back in service after three years. The experts say the crack gives the bell its unique but imperfect tone.

In more recent times, Big Ben stopped pealing for six weeks in 2007 and for repairs in 1983 and 1976. The bell was silent during the funerals of prime ministers Winston Churchill and Margaret Thatcher.

The keeper of the Great Clock explained that Big Ben must be silenced as the clock itself must be "dismantled piece by piece with each cog examined and restored."

The four opal glass faces of the dials will also be cleaned and repaired, the rusting cast iron framework renewed, and the hour and minute hands refurbished. In addition, some modern conveniences - like an elevator and washroom - will be built for the timekeepers.

While the refurbishment in ongoing, the conservationists will allow one dial of the four faces of the clock to be visible, so Londoners can still set their watches. A modern electric motor will turn the clock hands until "the prince of timekeepers" is repaired.

Washington Post