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The iconic electronic billboards of Piccadilly Circus were switched back on this morning in a test run after nine months of upgrade works.

Renovation work has converted six illuminated advertising boards into one ultra-high definition curved screen.

The screens went dark in January, marking the start of the longest blackout of the Piccadilly lights since the Blitz.

It was the first time they were switched off for an extended period of time since 1949.

Piccadilly Circus Lights 7 show all Piccadilly Circus Lights 1/7 Innovative: The Lights will be replaced with a screen that will have the highest resolution LED display of its size in the world. Lucy Young 2/7 Iconic: The famous Piccadilly Lights have only been turned off twice in the past. Yui Mok/PA 3/7 Lights out: The famous billboards, which were turned off on Monday in preparation for major redevelopment, will be back up and running in the Autumn. Dominic Lipinski/PA 4/7 Advertising: CocaCola renewed its deal with the Piccadilly Lights, where it has held an advertising space since 1954. Dominic Lipinski/PA 5/7 Lights out: The Piccadilly Lights will be replaced by one large single screen. Dominic Lipinski/PA 6/7 Famous: 100 million people pass through Piccadilly Circus and pass the lights each year. Lucy Young 7/7 Darkness: It is not known how much electricity will be saved during the break. Lucy Young 1/7 Innovative: The Lights will be replaced with a screen that will have the highest resolution LED display of its size in the world. Lucy Young 2/7 Iconic: The famous Piccadilly Lights have only been turned off twice in the past. Yui Mok/PA 3/7 Lights out: The famous billboards, which were turned off on Monday in preparation for major redevelopment, will be back up and running in the Autumn. Dominic Lipinski/PA 4/7 Advertising: CocaCola renewed its deal with the Piccadilly Lights, where it has held an advertising space since 1954. Dominic Lipinski/PA 5/7 Lights out: The Piccadilly Lights will be replaced by one large single screen. Dominic Lipinski/PA 6/7 Famous: 100 million people pass through Piccadilly Circus and pass the lights each year. Lucy Young 7/7 Darkness: It is not known how much electricity will be saved during the break. Lucy Young

During earlier testing last week, Twitter users expressed surprise at the dazzling brightness of the lights.

An estimated 100 million people pass through Piccadilly Circus every year, according to Landsec which operates the screens, making it one of the world's most prime advertising spaces.

The Piccadilly Lights will officially go live later this month.