Armed robbers stole a consignment of high-value computer equipment after threatening a van driver with a Taser gun.
The gang stopped a Ford Transit van carrying a shipment of electrical components at a bogus police census point at Stanwell Road near the junction with the A30 at Heathrow last week.
The robbers threatened one of the victims with a Taser gun and sprayed the driver with CS gas to force him out of the vehicle.
Metropolitan Police's Operation Grafton investigating officer Det Sgt Ian Wilson said, "These criminals were not afraid to use violence to carry out the robbery and the experience has left the driver and his passenger very shaken."
The back doors of the van had been forced open and the goods taken. Police have refused to identify the type of computer equipment stolen.