London landmark Big Ben fell silent for four years starting on Monday, as a political outcry mounted over renovations that will rob Britain of a cherished symbol at a time of national uncertainty.The 12 bongs from the famous bell rang out for midday in front of a hushed crowd of over a thousand people assembled in Parliament Square to mark the longest silence in its 157-year history."I can see it from where I live. I do live my life by it. I'm 72 and I'm worried it might be the last time I actually hear them!" said Denise Wiand, one of the spectators, who lives on the other side of the River Thames from parliament.Thomas Moser, a 54-year-old German tourist, said: "The crowd were really listening. We are here, we want to hear every single sound. It's almost a historical moment."Westminster's Elizabeth Tower, which looms over the Houses of Parliament and is one of Britain's most popular tourist attractions, is due for conservation work.The famous clock's bell has been stopped over health and safety concerns, silencing an emblem of continuity as Britain grapples with Brexit negotiations.The decision will protect builders working on the site, amid fears that prolonged exposure to the 118-decibel bongs from the 13.7-tonne Big Ben bell, which chimes out the hour, could damage hearing.But the debate has swiftly moved into the political sphere.The shutdown will coincide with Britain's impending departure from the European Union, a period set to be politically turbulent and economically fraught.The bongs are a venerated part of British life, used at the start of radio and TV newscasts and the midnight countdown to New Year's Day. The sound is also familiar to many people beyond Britain, as it is broadcast on the BBC World Service.Pro-Brexit members of parliament have criticised the decision to shut down the chimes.Prime Minister Theresa May is among those who have raised concern. "Of course we want to ensure people's safety at work, but it can't be right for Big Ben to be silent for four years," she told reporters.She said she hoped a House of Commons commission would "look into this urgently so that we can ensure that we can continue to hear Big Ben through those four years."The Commons has said that it "will consider the length of time that the bells will fall silent". "Of course, any discussion will focus on undertaking the work efficiently, protecting the health and safety of those involved, and seeking to ensure resumption of normal service as soon as it is practicable," it says.Under the plan, a lamp at the top of the neo-Gothic bell tower that is turned on when parliament is sitting is also set to be turned off for the first time in more than 70 years, but it is not yet known when it will go dark, or for how long it will be off.Andrea Leadsom, the Leader of the House of Commons, held emergency talks on Friday with Speaker John Bercow, who chairs the Commons panel that approved the measures. The commission has agreed to meet next month to review whether the bongs can be heard on certain exceptional days.Under current plans, the bell would still ring on occasions such as Remembrance Sunday in November, which commemorates Britain's war dead, and New Year's Eve.Three MPs from May's Conservative Party are calling for the clock to be back in action on the eve of March 29, 2019, when Britain is due to leave the European Union."It would be very fitting if Big Ben was to chime us out of the EU. We need to go out with a boom as we regain a sovereign parliament once again," said MP Andrew Bridgen.The 96-metre tower is the most photographed building in Britain. The renovation is estimated to cost US$37 million. But politicians have claimed that when they agreed to the work, they did not know the chimes would be silenced for four years.A YouGov poll published Saturday found that 44 per cent of Britons believe Big Ben should be silenced during the renovations, except for special occasions, while 41 per cent said it should operate as normal.Some MPs have suggested the bell could ring outside of the conservation team's working hours.But the House of Commons said that starting and stopping the clock takes about half a day, and that this would be neither practical nor "a good use of public money".