Big Ben is about to fall silent for the longest period in its 157-year history as part of a vast four-year repair project.
The bell's famous bongs will stop at noon next Monday 21 August - and apart from New Year's Eve and Remembrance Sunday, they will not ring out through Westminster again until 2021.
The 315ft, Grade I listed Elizabeth Tower that holds the bell and clock face is undergoing what House of Commons officials claimed would be a £29million restoration.
But there are now fears the cost of the revamp on the crumbling Parliamentary estate has soared.
Reports earlier this year claimed the cost to taxpayers had doubled to £60million.
Now Commons officials have admitted they will make an "announcement" later this year revealing the final cost of the work - and are refusing to give a figure until then.
The tower is the centrepiece of Westminster and a popular tourist sight
The only contract that has been signed for the work is one for putting up the scaffolding, with construction firm Sir Robert McAlpine.
Firms are still bidding for the final contract to carry out the actual work.
A House of Commons spokesman said: "Due to strict confidentiality rules we are unable to comment on the process (including the project budget and timeline) further at this time."
The tower's 13.7-tonne Great Bell - it, not the tower, is nicknamed Big Ben - has marked the hour on the note of E with "almost unbroken service" since 31 May 1859.
The bell was the largest ever cast in east London's Whitechapel Bell Foundry, which also cast the Liberty Bell and still runs today after nearly 500 years.
Ben Ben last fell silent for maintenance in 2007 and a major revamp between 1983 and 1985.
It also fell silent during the two world wars - but a Commons spokesman confirmed it is expected to be longest period without hourly chimes since they began in 1859.
Big Ben on VE Day in 1945. It is the longest silence of hourly chimes in its history
The bell's silence will be to "ensure the safety" of workers repairing the tower.
Its chiming relies on gravity so the hammers that hit the bell will have to be locked, and the bell disconnected from the rest of the mechanism.
The tower's famous clock faces will be mostly obscured by scaffolding as soon as October this year.
Parliamentary officials have assured the public one of its four faces will always be visible - but the other three will be covered.
The mechanism of the clock itself will also stop for "several months" as part of the project. Until now, Parliamentary officials had only confirmed this period would see chimes stop - but now they will stop for four years.
The project is not part of a wider revamp of the Palace of Westminster which could cost £4billion or more and is due to start in the 2020s.