The billboard lights of Piccadilly Circus were switched back on following major renovations.
The sample, which has been shown to electric power ads for more than a century, was shut down in January and replaced with a temporary banner.
The new state-of-the-art screen is interactive and fully responsive that allows advertisers to include aspects such as streaming live video.
Around 100 million people are pushed into the centre of London site each year.
Before January it was the first time since the second World War, the lights were off, apart from that during power outages and special events.
The poster above six LED screens have been replaced by the largest single screen in Europe, measuring about 780 square metres (8,400 sq ft) in size.
The screen has about 11.6 million light bulbs, the improvement of the quality of the images on the screen.
A crib has also been installed on the roof to clean and maintain the LED panels that are expected to last for the next 10 years.
Six of the advertisers share the space and the new technology allows them to modify the content based on the surrounding environment, according to the site owners Land Securities.
For example, if the temperature falls below a certain level, ads for winter clothing, you can go on the screen instead of summer.
A Land Securities spokesman said that “a complex content management system” had been developed to “basically manage six live Tvs that have the ability to move around the screen and change of place.”
The first marks are displayed in the new poster for Coca-Cola, which has been advertising in the area since 1954, and Samsung.
Perrier was the first brand to always be illuminated in Piccadilly, while BP, Panasonic, Cinzano and TDK also displayed ads in the past.
The light of the history
1819 – Piccadilly Circus is built to connect Regent Street with Piccadilly
1908 – electric ads appear, with Perrier the first brand to be illuminated
1923 – Electric billboards located on the faÃ§ade of London Pavilion to advertise Bovril
2011 – LED displays completely replace neon lamps