Around 120 firefighters and 20 fire engines have been called to a blaze at a five-star hotel in central London.
Huge plumes of smoke were seen coming from the Mandarin Oriental building in Knightsbridge.
London Fire Brigade said it was called shortly before 4pm and the cause of the flames was not yet known.
Twenty fire engines are at the scene including crews from Chelsea, Kensington, Hammersmith and Battersea.
London Ambulance Service said it had sent a number of resources to the incident including its hazardous area response team.
Staff from the Mandarin Oriental hotel, which was recently completed the most expensive renovation in its 115-year history were evacuated to Hyde Park where they were being given bottles of water.
One worker, who asked not to be named, said: “The fire alarm started and everybody was told to get outside.
Everything’s fine but we don’t know how it started yet.
TV presenter Anna Whiteley said she was evacuated from the hotel, adding that she was “so impressed by the organisation in bringing everyone to safety”.
As the situation is still unfolding, we have no further details to share at this time, but will provide an update soon.
Witness reported that the fire could be seen in the middle floors of the 12-storey building, while a tradesman working at the hotel said he “could see orange flames on the roof”.
The Mandarin Oriental describes itself on its website as one of London’s most celebrated five-star hotels that exudes an enticing mix of elegance and luxury.
It has recently completed a multi-million pound renovation and has a number of luxury restaurants including Dinner by Heston Blumenthal.
The historic, Edwardian-style building was first opened as the Hyde Park Hotel in 1902 before it was bought by Mandarin Oriental Hotel Group in 1996.
Designer Joyce Wang was tasked with transforming all 181 bedrooms and public areas.
In 1899, a major fire struck the building which damaged the top three floors of the Knightsbridge wing and destroyed part of the roof. There were no fatalities or injuries in the incident.