The London Fire Brigade said this afternoon that more than 120 firefighters were working to quash the blaze at the hotel on Chiltern Street.
The statement read: “Twenty fire engines and around 125 firefighters have been called to a fire at a hotel on Chiltern Street in Marylebone.
“There is a fire in ducting which leads from the ground floor to the roof of the four storey hotel with a restaurant on the ground floor. A plant room at roof level is also alight.
“Around one hundred people have evacuated the building before the Brigade arrived.
“The Brigade’s 999 Control officers were first called at 1452 and deployed fire crews from Euston, Soho, Paddington, Soho, West Hampstead, Kensington and Chelsea fire stations and are still at the scene.
“The cause of the fire is not known at this stage.”