London (AFP) - Wearing ear plugs to muffle the chimes of Big Ben, a team of abseilers is busy this week cleaning the clock faces at the Houses of Parliament in London.
Wearing hard hats and armed with buckets and cloths, the four specialist technicians are descending the London landmark by rope to clean and inspect the four clock faces.
The clock faces on the Elizabeth Tower were last cleaned in 2010 and besides getting rid of any dirt that has accumulated since then, the experts are conducting a photographic survey to check the dials for damage.
"Big Ben is one of the UK's greatest icons, and cleaning the Great Clock is a vital part of its maintenance," said Steve Jaggs, deputy keeper of the clock.
"The process is complex and requires a real head for heights. We have an expert team who will ensure that the clock is thoroughly cleaned and that this piece of our national heritage is safeguarded for future generations."
Each clock face is made up of 312 pieces of white opaque glass, held together by a cast iron framework.
The clock inside the tower continues to keep time during the cleaning process but the hands on the face being washed are set at 12 to make it easier for the technicians to clamber around.
Five days have been set aside for the job -- one for each of the four clock faces, with a contingency day in case the weather makes it too risky to work.
Big Ben is the name of the huge bell at the top of the 96-metre (316-foot) high tower, but is often used to refer to the tower itself, which looms over the 19th century Gothic Revival parliament.
The tower was constructed as part of the reconstruction of the Houses of Parliament by architects Charles Barry and Augustus Pugin following a major fire in 1843.
There are two theories of how the bell came to be known as Big Ben.
The most likely explanation is that it was named after Benjamin Hall, the engineer whose name is inscribed on the bell, but some believe it is named after Ben Caunt, a champion heavyweight boxer of the 1850s.
The bell, with its distinctive "bongs", sounds out the hours over central London with different chimes to mark every quarter of the hour.