Ten fire engines and over 70 firefighters and officers were called to a fire in offices on Strand-On-The-Green in Chiswick during the early hours of this morning.
The first floor and roof of the building were badly affected by the blaze.
Station Manager Carl St Paul who was at the scene said: "Our crews worked extremely hard in challenging conditions to get this fire under control and to stop it from spreading to neighbouring properties. Thankfully no-one was inside the office building when the fire broke out but around 12 people from homes close by were evacuated during the incident as a precaution."
London Ambulance Service treated a man at the scene for a non fire related illness.
The Brigade was called at 0018 and the fire was under control by 0430.
Crews from Acton, Chiswick, Richmond, Heston, Ealing, Kingston, Kensington, Southall and Hammersmith fire stations attended the incident. An aerial ladder platform and turntable ladder were also called on to the fire to fight the blaze from above.
Firefighters will remain at the scene for some time this morning damping down the fire. The cause is under investigation.