Fifteen fire engines and around 100 firefighters were called to a fire at a spa building adjoining a hotel in Richmond Hill in Richmond.
A leisure complex and pool building was destroyed by fire. Part of the third floor and roof of the adjoining hotel annexe were also damaged by fire.
Station Manager Mike Cotton, who was at the scene, said: "Firefighters worked hard in very challenging conditions to bring the fire under control. Crews were at the scene working throughout the day to extinguish remaining deep seated pockets of fire.
"The fire was in an annexe building and produced a lot of smoke.
"Local road closures were in place and we advised drivers to avoid the area if possible and to check their journey before travelling."
Approximately 300 people left surrounding buildings as a precaution and hotel guests were provided with alternative accommodation. There were no reports of any injuries.
The Brigade was called at 1824 and the fire was under control at 0136 (May 1). Fire crews from Richmond, Twickenham, Kingston, Heston and other surrounding fire stations attended the scene.