Four fire engines and around 25 firefighters were called to a fire at a golf club house in Richmond Park in Richmond.
Part of the living grass roof of the building was damaged by fire. There were no reports of any injuries.
The Brigade’s Fire Investigators believe the fire was accidental and caused by a smouldering disposal barbecue bag being carried by the wind and on to grass on top of a roof.
A London Fire Brigade spokesperson said: “During this warm weather that we have been having, the ground becomes extremely dry and grass can burn quickly.
"Disposable barbecues can cause fires when smouldering ash and embers are carried by the wind onto areas of dry grass.
"Disposable barbecues that have been discarded and abandoned can still end up causing a fire as they will continue to retain heat after use – they need to be put right out and cooled before being thrown away.
“Always make sure barbecues are not left unattended and check barbecues are completely out when you have finished and never leave it to smoulder as they stay hot for a long time.”
The Brigade was called at 1646 and the fire was under control by 1743. Fire crews from Wandsworth, New Malden, Fulham and Kingston fire stations attended the scene.