Dozens of firefighters tackled a massive blaze at a Michelin-starred restaurant in Mayfair.
Photos and videos posted on social media showed thick grey smoke billowing from a building after the fire broke out on Thursday afternoon.
One witness said people had to take cover while ash fell from the sky.
In one clip, smoke could be seen emerging from the entrance to Indian restaurant Gymkhana.
The London Fire Brigade said half of the restaurant's ground floor kitchen and half of the ducting from the ground floor to roof level was alight.
Eight fire engines and 60 firefighters were called to the inferno in Albemarle Street just after 4pm.
It was under control by 6.30pm, with no injuries reported.
Eyewitness Greg Power told the Standard: "I work in Old Bond Street and stepped out of the office for some fresh air, when I noticed this big plume of smoke.
"I walked down Stafford Street and saw the firefighters going into Gymkhana.
He added: "It seems the fire started in the kitchen and then spread through - it looked like a pretty nasty one."
Mr Power went on: "It was very intense. People were stepping back as big lumps of ash came down.
"I saw my white shirt was also getting covered with ash, so I thought it was best to walk away."
The cause of the fire is unknown.
Fire crews from Soho, Lambeth, Kensington, Euston, Paddington, Chelsea and Dowgate fire stations were at the scene.
