A hundred firefighters battled a fire at the Richmond Harbour hotel and spa through the night, evacuating about 300 people from the property and surrounding buildings.
London Fire Brigade was called to the blaze at 6.24pm yesterday and worked into the early hours, bringing it under control shortly after 1am.
Crews found the roof of the spa building was entirely ablaze with the fire having spread to part of the third floor of the adjoining hotel, which was acquired by the Harbour Hotels group in 2017.
Station manager Mike Cotton said: "Firefighters worked hard in very challenging conditions to bring the fire under control. We expect to be at the scene working throughout the day today (1 May) to extinguish remaining deep seated pockets of fire.
"The fire was in an annexe building and had been producing a lot of smoke. Local road closures remain in place so we would advise drivers to avoid the area if possible and to check their journey before travelling."
Hotel guests have been provided with alternative accommodation and there are no reports of other injuries. The hotel is now expected to remain closed to guests until next Monday.
A spokesperson for Harbour hotel group said: "It is with regret that a fire at the Richmond Harbour Hotel Spa has caused extensive roof damage.
"The cause is as yet unknown, but maintenance was being carried out on the roof by external contractors. Fortunately, due to the efforts of the emergency services, the damage was largely contained to the Spa and we are extremely grateful."
The group praised the professionalism of its staff who led the evacuation and said work would commence "imminently" to restore the building.
The group added: "We would like to thank everyone involved in containing the incident and apologise for any inconvenience caused to our friends in Richmond."
The cause of the fire is under investigation.
Harbour Hotels group was created in 2003 by chairman Nicolas Roach and now has 16 sites across the south of England.
Images: London Fire Brigade