London radio station Capital FM has launched a campaign calling on all Londoners to switch off their lights for an hour on the longest day of the year.
The station is asking those living in the capital to power down between 8pm and 9pm on Thursday, June 21.
According to the station's calculations if the lights were turned off in 3 million homes, this would save around 750MWh.
The campaign has been endorsed by celebrities, businesses and those responsible for famous landmarks around the capital.
Lights out for London
