A power cut plunged parts of central London into darkness during the Black Friday shopping holiday.
The West End and Soho districts - both of which were full of shoppers, tourists and people on nights out at the time - went dark shortly after 5pm.
The famous electric billboards of Piccadilly Circus shut down, leaving the cross section in shadows.
UK Power Networks explained "engineers are now on site" investigating the cause of the sudden blackout.
Engineers were able to get some power back to the affected area by re-routing around the fault. UK Power Networks estimated full power would return between 8:30pm and 9:30pm.
The evening West End performance of Aladdin the Musical was cancelled due to the power cut.
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."
Transport for London explained the tube network was not affected by the power cut but said travellers were held at Tottenham Court Road and Oxford Circus stations to avoid overcrowding.
Blackout witness 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."
