Two lanes of the M25 clockwise between junctions 24 and 25 have been closed following an accident.
There is two and half miles of traffic on the stretch of road between Potters Bar and Enfield.
It has been reported the 84 bus service is delayed because of the accident.
It is not known when the traffic will have cleared by.
There has also been an accident on the A1 southbound entry slip from the M25.
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