The clock is original Victorian the mechanism was repaired as part of a huge restoration project, and the scaffolding surrounding the tower was gradually demolished from December 2021.
House of Commons Speaker Sir Lindsay Hoyle said the clock change “signals a new beginning” for the central parliament. London landmark
Parliament’s team of clock mechanics will need a total of 24 hours over the weekend to ensure that all 2,000 clocks across the estate are moved in time for the clocks to return on October 30.
Over the past five years, the Elizabeth Tower, as well as the clock and bell mechanisms in it, underwent the largest repair and conservation in its entire 160-year history.
The tower at the north end of the Houses of Parliament, also known as Big Ben after the bell inside, was covered in scaffolding during restoration work.
Sir Lindsay said: “While we are all tucked up in our beds, our very own father (clockmaker) Ian Westworth and his team will be tracking eight miles moving our Parliament clocks, including the one we love most, the Great Clock of Westminster , better known as Big Ben.
“For the first time in five years they will be working with a complete original Victorian clock movement, so this is an important final step in the preservation of this magnificent timepiece.”
It will be the first time the clock has been converted to GMT since it was restored and installed in the tower earlier this year.
Sir Lindsay added: “Big Ben’s bongos will return to our national soundtrack on Armistice Day and Remembrance Sunday, striking 11 times to mark the start of the two minutes’ silence.”
People will only know that Big Ben switches to GMT when the lights on the four dials go out at 10pm on Saturday.
Parliamentary clock mechanic Alex Geoffrey said: “This is so people don’t look up and wonder why the hands are spinning and getting confused.
“Under cover of darkness, we actually stop the clock and keep it running for two hours, only restarting it again at midnight and turning the dial lamps back on again at 2 a.m., which is officially GMT.”
Every year during the winter time, the hands of the clocks are turned back so that people can start and end the work day an hour earlier.
This means that people have an hour less daylight at the end of the day, which may be less practical in the winter when it gets darker in the evenings.
The clock was designed and installed in 1859 with the aim of creating the most accurate public clock in the world.
When the black paint was removed from the dials during renovations last year, it was discovered that they had originally been painted in a color known as Prussian blue.