A fire which broke out at The Dorchester Hotel on Tuesday began in the building’s extraction system, investigators have said.
Hot particles from a round saw got into the filter system and set fire to debris in the ducting at the Mayfair establishment on Park Lane.
Hundred guests were ushered out of their luxury suites within minutes after the flames took hold in the basement of an adjoining staff block.
Four fire engines and 25 crew were sent to the hotel which remains popular among film stars, writers and celebrities.
The Dorchester told the Evening Standard no guests were injured and the establishment remains “open as usual”.
A spokesperson added: “There was a small, contained fire in a back of house area at The Dorchester at approximately 3.15pm on August 31.
“The alarm was raised, the hotel fully evacuated, and the fire quickly extinguished.”
London Fire Brigade (LFB) was called at 3.15pm and had the blaze under control within two hours.
Bishopsgate City of London Cllr Shravan Joshi, who was staying at the hotel with his wife, praised the evacuation effort.
“You guys are amazing, evacuated the hotel in minutes,” he tweeted.
“Such a swift response. Hope everyone is safe and sound.”
Fire crews from Chelsea, Soho and Paddington fire stations attended the scene as guests crowded at the front of the hotel.
All guests and employees returned to the hotel which resumed normal operations following a full investigation.
The world famous hotel also hosted Prince Phillip’s secret stag-do before his marriage to the Queen in 1947.