A power cut has plunged parts of central London into darkness.
It has hit the busy Soho entertainment district, which is packed with tourists, Black Friday shoppers and people out to enjoy the nightlife.
UK Power Networks said that "engineers are now on site" and have started investigations in to the cause of the blackout.
People at the scene posted images on social media of darkened streets, and Piccadilly Circus with many of its famous lights extinguished.
Theatregoers heading for the West End performance of Aladdin the Musical were told it had been cancelled.
A spokesman for the Disney West End musical, playing at the Prince Edward Theatre, tweeted: "Due to the ongoing power cut in Central London we regret that tonight's performance has been cancelled. Tickets will be refunded. Please refer to your original point of purchase for full details. We regret any disappointment or inconvenience caused by this unavoidable occurrence. Thank you."
The power cut meant that the bright lights of billboards in the West End went out, while rush hour commuters and office workers found themselves in darkness.
Passer-by Adrie van der Luijt tweeted: "You can't see where you are walking throughout Soho, Shaftesbury Avenue, Piccadilly Circus and Chinatown. Astonishing. No traffic lights."
Transport for London said the Tube network has not been hit by the powercut but that travellers had been held at the stations such as Tottenham Court Road and Oxford Circus to prevent overcrowding.
UK Power Networks later tweeted that engineers had been able to get some power back on to the area by re-routing around the fault. Engineers estimated that power would be back on between 8.30 and 9.30pm.