A barn on a historic site in Joel Street, Northwood Hills, has been destroyed by fire.
The blaze started at about 10.45pm a the barn on the Joel Street Farm site.
Firefighters were still on the scene at 10am damping down and a tractor was dragging the bales away from the smouldering building.
Neighbours told the Gazette that they heard a crackling noise as the fire started.
One said: "I realised it was a fire and called the police and fire brigade.
"They came with an ambulance and the police were directing traffic away."
Two people escaped before the fire brigade arrived and were treated on the scene for smoke inhalation by the London Ambulance Service.
A horse, whose stable was very close to the barn, was rescued and taken to safety, and several other horses in a nearby field were protected by crews working with the police.
An LFB spokesman said the barn, which contained about 100 tonnes of straw and hay bales, was completely destroyed.
Four fire engines and around 20 firefighters from Ruislip, Harrow, and Northolt fire stations attended the scene.
The call came at 10.47pm and the fire was under control by 2am. Crews remained at the scene throughout the night to dampen down hot pockets and make sure the fire did not reignite, the spokesman said.
The cause of the blaze is under investigation.
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