A motorcyclist has died in a horror accident with a van on the M4 near Heathrow Airport.
And the crash at roughly 1.45pm has closed the key motorway in both directions causing massive queues up to seven miles long.
Motorists have been advised to avoid the area.
Met Police wrote on Twitter: "Male motorcyclist fatally injured following collision with a van.
"Driver of the van stopped at scene, no arrests.
"Significant travel disruption, roads closed both directions. Pls use alternate routes."
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The eastbound carriageway is expected to be closed for several hours while investigations are carried out at the scene.
On a bridge across the motorway bottles of water are being dropped down to help stranded motorists getting dehydrated in the warm weather.
The disruption is also causing problems on the M25 in both directions between junctions 14 and 16.
The M4 closure is likely to cause problems for drivers from Reading, Berkshire trying to get towards London.
A spokesman for the London Ambulance Service said: "We were called at 1.27pm today to the M4 near Harlington to reports of a road traffic collision.
"We dispatched an incident response officer, two medics in response cars and an ambulance crew. We also dispatched London’s Air Ambulance.
"Sadly a person was pronounced dead at the scene."
