All four faces of Big Ben will be put back to Greenwich mean time (GMT) this weekend for the first time in five years.
British summer time (BST) officially ends at 2am on Sunday, and the clocks go back an hour, giving people an extra hour in bed – or partying.
The Great Clock on the Elizabeth Tower, better known by the name of its bell, Big Ben, will be changed in the early hours of Sunday morning.
The Commons Speaker, Sir Lindsay Hoyle, said the clock change “will herald a new beginning” for the landmark at the northern end of the Houses of Parliament.
It will take parliament’s team of clock mechanics 24 hours over the weekend to ensure that all 2,000 timepieces across the estate are changed in time for the clocks to go back.
The Elizabeth Tower, the clockwork and bell mechanism have been covered in scaffolding over the past five years while undergoing the biggest repair and conservation work in its 160-year history.
Hoyle said: “While the rest of us are tucked up in our beds, our own father time [clock maker] Ian Westworth and the team will be clocking up 8 miles changing our parliamentary clocks, including the one we love the most, the Great Clock of Westminster, better known as Big Ben.
“For the first time in five years they will be working with the clock’s completed original Victorian mechanism, so it is a significant final moment in the conservation of this magnificent timepiece.”
It will be the first time the clock has been put back to GMT since it was restored and installed in the tower earlier this year.
People will only be aware that Big Ben is being changed to GMT when the lights go out on its four dial faces at 10pm on Saturday.
The parliamentary clock mechanic Alex Jeffrey said: “This is so people looking up do not wonder why the hands are going round and get confused.
“Under the cover of darkness we effectively stop the clock and hold it for two hours, only restarting it again at midnight and putting the dial lights back on at 2am when it is officially GMT.”
The clock was designed and installed in 1859, with the aim of creating the most accurate public timepiece in the world.
When black paint was stripped away from the dials during repair work last year, it was discovered that it was originally painted in a colour known as Prussian blue.
