A major fire that broke out at a high-voltage electrical substation near Heathrow Airport has finally been extinguished, six days after it ignited late on the night of 20 March.

London Fire Brigade (LFB) confirmed that the fire, which began at 23:23 on 20 March, was initially brought under control by 06:28 the following morning. However, lingering hotspots within the heavily insulated and oil-fuelled transformer required days of careful monitoring and technical firefighting operations.

The blaze involved a transformer containing insulating oil, a key risk factor in such incidents due to its flammability and the high voltage of surrounding equipment. Firefighters initially used foam to suppress the flames and later employed indirect cooling methods with misting jets to reduce the heat when direct access was too dangerous.

To tackle the complexity of the blaze, the LFB deployed ten fire engines, two Bulk Foam Units, and a High Volume Pump, with around 70 firefighters on scene at its peak. The Brigade’s drone team played a critical role in providing aerial video and thermal imaging to identify remaining hotspots, helping crews strategically target inaccessible pockets of fire.

As a precaution, a 200-metre cordon was put in place, and approximately 150 people were evacuated from nearby homes. Thankfully, no injuries were reported.

Speaking after the operation was concluded, Deputy Commissioner Jonathan Smith praised the work of the emergency services:

“Our firefighters worked tirelessly in challenging and hazardous conditions overnight to bring the fire under control as swiftly as possible. I would like to take this opportunity to thank firefighters, Control officers and staff for their courage and professionalism in bringing this incident under control.”

Due to the hazardous materials involved and the fire’s proximity to sensitive infrastructure, the Metropolitan Police declared a major incident at 00:42 on the night of the fire.

Since then, fire crews remained on site to manage the scene and ensure any remaining embers were dealt with safely. As the oil levels in the transformer dropped, LFB teams switched to a more aggressive approach on Wednesday, 26 March, deploying ground monitors and water branches to deliver a final push to extinguish the fire.

A joint investigation between London Fire Brigade Fire Investigation Officers and the Met Police has ruled out foul play, with the cause believed to be related to electrical equipment failure. LFB will continue its investigation, supported by Fire Safety Officers under the Regulatory Reform (Fire Safety) Order 2005.

Local residents can now return to normal after a tense week, and the area is expected to fully reopen once the final stages of the investigation are complete.