Nearly 100 firefighters were needed to put out a large grass fire near Heathrow Airport.
Fifteen fire engines had been sent to the blaze, in Staines Road, Feltham, which broke out at about 16:00 BST.
Grass land the size of five football pitches was damaged by fire and 14 horses were removed from a nearby field, London Fire Brigade said.
A spokesman for Heathrow Airport said the fire had "no impact" on its flights and both runways ran as normal.
There have been no reported injuries.
The cause of the fire was not yet known but a spokeswoman for the fire service said it was likely to be related to the long stretch of dry weather.
She added it was difficult to say when the fire would be out, adding, "grass fires are very unpredictable".
London fire brigade is warning people to discard cigarette ends and glass containers in bins.