LONDON (Reuters Life!) - Three times a week, clock maker Paul Roberson climbs the 334 steps to the top of the Clock Tower in London to wind up and adjust arguably the world's most famous timepiece.
Commonly called Big Ben, which is actually the nickname of the bell inside it, the 96-meter tower looks down on the Houses of Parliament along the River Thames and has become a symbol of stability, endurance and democracy in Britain.
It was 150 years ago on Sunday that the four-faced Great Clock started keeping time, and on July 11, 1859, Big Ben first struck time.
"The clock is 150 years old and still weight-driven so it's weights that are driving the clock and those weights slowly work their way down to the ground," Roberson told Reuters inside the tower, against a backdrop of cogs and wheels driving the hands on the famous iron and opal-glass clock faces.
"After three days they're on the ground so we have to come up her three times a week and wind them back up again exactly like 150 years ago when the clock was first installed."
Roberson uses old pennies balanced on top of the pendulum to slow the clock down or speed it up, depending on whether it is running fast or slow.
"By adding a penny we can speed the clock up two fifths of a second a day, take the penny off and it slows it down ... that's how we keep the clock spot on.
"It's always within a second a day so we're monitoring that all the time and we can make small adjustments if necessary."
Big Ben became established as an international celebrity with the advent of radio.
On New Year's Eve 1923, the Great Bell was heard for the first time on the BBC. A microphone placed inside a football bladder was installed in the belfry, providing direct transmission to the BBC control room at Savoy Hill.
Soon after, it became a regular feature on the airwaves. In 1932 Big Ben went global when the BBC started their Empire Service, later called the World Service, which reached millions of people throughout the British Commonwealth.
The arrival of television only added to its fame -- the clock face made its first television appearance on a New Year's Eve program in 1949 and Big Ben has continued its starring role ever since.
Roberson says the clock tower, clock and bells have become powerful symbols in Britain.
"It brings a lot of affection to a lot of people," he said.
"Especially during the war they introduced the silent minute at nine o'clock. When the clock struck nine everyone would be silent for a minute and remember people during the war.
"Even today we bring people up here and they get very emotional about it."
Parliament Square, and the Clock Tower which looks down on it, remain favorite stop-offs for tourists in London.
"I remember Peter Pan when he stood on the clock," said Paola, from Mexico, referring to the Disney cartoon classic.
Judy, from the United States, added: "It is suggested that you make a 'phone call home just as it is about to sound so that you can say guess where I am ... 'bong, bong!"
Writing by Mike Collett-White; Editing by Steve Addison