Ten fire engines and around 70 firefighters tackled a pub fire on Conway Street in Fitzrovia.
The extraction system from a kitchen on the first floor to the roof vent was destroyed by fire. Part of the first, second and third floors and part of the roof of the building were also damaged by the blaze.
The fire was discovered when a member of staff heard a noise in the extraction unit above a wood and charcoal grill in the kitchen.
Station Commander Jason Fisby said:
"The fire was within the extraction system from the first floor to the roof vent. There were no reports of any injuries.
"Access to the seat of the fire was challenging and very labour intensive. The number of fire engines at the scene was a reflection of the need for a high turn over of firefighters wearing breathing apparatus.
"Firefighters carried out salvage work and trying to prevent water damage on the floors below."
The Brigade's Fire Investigators believe the fire was caused by a spark from burning wood in a grill igniting fat deposits within the extraction unit.
The Brigade was called at 1215 and the fire was under control by 1548. Fire crews from Islington, Kentish Town, Euston, Soho and Paddington were at the scene.