Lights on the six billboards went dark on Monday morning so the property company that owns the popular tourist site can replace them with a state-of-the-art single digital screen.
According to the owner, Land Securities, the 784-square-meter screen will be the largest in Europe and will retain the curved shape and patchwork appearance of the current lights.
When the lights go back on in the fall, they will be linked to a high-speed Wi-Fi network and be able to live-stream events from across the globe.
During the redevelopment work, the area will be covered by an advertising banner that won't change.
The busy intersection in London's theater district -- which sees millions of people pass through it each year - has been famous for its lights for more than a century.
The first illuminated lettering was attached to buildings there in the late 1890s, according to documents from the former London County Council
, which has owned the famous landmark since 1968, says the first illuminated advertising billboard was a Perrier sign erected in 1908.
Light bulbs were gradually replaced with neon lights, with the first digital projectors introduced in 1998.
The last time the lights were turned off for an extended period, during World War II, the aim was to hamper German bombers.
Since then, they've only been dimmed for brief periods -- such as occasional blackouts, and to mark the funerals of Winston Churchill in 1965 and Princess Diana in 1997.
Vasiliki Arvaniti, portfolio manager at Land Securities said in a statement Monday: "This is a huge day for Piccadilly lights and though it will be a strange feeling to see them go dark, we're incredibly excited about their future."
"There have been illuminated advertising signs at Piccadilly Circus for more than a century," he said, "and the new state-of-the-art screen we're installing will stay true to its tradition as a site for advertising innovation by offering brands pioneering new ways to connect to the 100 million people who pass by each year."