Big Ben means so much to so many - and it's our job to make sure it tells the right time'

On Saturday night Steve Jaggs will do something both very special and rather mundane.

Like millions of people around the country he will put his clock back an hour. But unlike them it will take five hours to complete the operation, rather than just a few minutes.

That is because Mr Jaggs is responsible for putting back the hands not just of any clock, but of Big Ben, arguably the most famous chimes in the world.

At 2am on Sunday morning the quarter bells on the Great Clock at the Palace of Westminster will sound and the Great Bell – or ‘Big Ben’ as it is known by millions– will strike the hour, signalling the end of British Summer Time and the start of Greenwich Mean Time.

It will be the culmination of a long and delicate process to put the clock’s huge mechanism back by an hour.

This involves locking Big Ben to prevent it ringing and stopping the giant hands, advancing them to 12 and restarting the clock at the new midnight, one hour behind the old.

Steve Jaggs, Keeper of the Great Clock of Westminster   Photo: Stella Pictures

Throughout the entire operation - in which the clock's mechanism is fully inspected - the dozens of 85w bulbs which light up each of the clock’s four faces are switched off, so that passing members of the public are not confused by the time being set at midnight for several hours.

“It’s a job that makes us all very aware of how much people rely on Big Ben,” said Mr Jaggs. “It’s a clock that means so much, to so many people, not just in Britain but around the world.

“It’s such a recognisable symbol, in whatever language people speak, of London, of the mother of all Parliaments, of democracy.”

It’s not just Big Ben that Mr Jaggs, the Keeper of the Great Clock, has to worry about. There are more than 2,000 clocks in the Palace of Westminster, hidden in the halls, chambers and dusty committee rooms of the Houses of Parliament, and each one has to be put back.

Steve Jaggs, Keeper of the Great Clock of Westminster looks on next to Big Ben as it has its time changed for winter at the Houses of Parliament  Photo: Stella Pictures

It takes the Palace’s clockmakers and their assistants two days to adjust them all, starting on Saturday morning and not completing their task until Sunday evening.

Working in shifts, three teams of three clockmakers and their assistants scour the corridors, poke into rooms and climb on stepladders to reach each clock.

Steve Jaggs, Keeper of the Great Clock of Westminster   Photo: Stella Pictures

Several of the clockmakers have worked at the Palace of Westminster for over a decade and they take a pride in knowing the individual quirks and intricacies of each of their timepieces.

So, while every household in the country will be relying on someone having remembered to put the clocks back tonight, MPs and Lords will be able to return to the Houses of Parliament on Monday secure in the knowledge that the clocks will tell the right time.

Steve Jaggs, Keeper of the Great Clock of Westminster looks on next to Big Ben as it has its time changed for winter at the Houses of Parliament  Photo: Stella Pictures

The time change comes amid fears for the future of Big Ben, with the Commons finance committee warning that the taxpayer faces a bill of at least £29m to properly refurbish the clock and keep the famous “bongs” sounding into the future.

A complete overhaul could see the mechanism shut down for around four months, for what would be the longest stoppage in its 156-year history.

According to a document written for the committee, “the clock currently has chronic problems with the bearings behind the hands and the pendulum either could become acute at any time, causing the clock to stop – or worse”.

Steve Jaggs, Keeper of the Great Clock of Westminster looks on next to the dial as it prepares to have its time changed for winter at the Houses of Parliament  Photo: Stella Pictures

Action is also needed to combat “severe metal erosion, cracks in the roof and other structural defects” in the Elizabeth Tower, which houses the Great Clock.

But the men and women who look after Big Ben are sanguine about its prospects, saying that while it requires constant care and attention, for a machine that is nearly 160 years old it is in remarkably good shape.

Ninety per cents of its parts are the original pieces assembled and installed in April 1859, at a cost of £2500, with others replaced after they were accidentally damaged during repairs in 1976.

“Sometimes it just stops,” admitted one of the clockmakers. “If the oil thickens up, or the parts expand or shrink too much on a particularly hot or cold day, it may stop one of the bells working. But that happens very rarely.”

Steve Jaggs, Keeper of the Great Clock of Westminster looks on next to Big Ben  Photo: Stella Pictures

As they climb the 334 steps of the Elizabeth Tower to reach the room housing the Great Clock’s mechanism, on Saturday night, Mr Jaggs and his team will be all too aware of the importance of their role in keeping Big Ben’s bong going – and telling the right time.

“I can step out of here at any time on any day and there will be someone taking a picture of Big Ben,” he said. “It’s a hugely significant part of so many people’s heritage that we are looking after and we’re very proud of that.”