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Part of the motorway was blocked after a five-car collision.
There was a crash on the A2 London bound between the B255 Bean and J2 of the M25, near Darenth Interchange.
A man who was trapped in one of the vehicles was freed by the fire service.
Drivers were told to expect delays as they could only use the slip road onto the M25 and A282 anti-clockwise.
The fire service said a lorry was involved in the collision and crews used hydraulic rescue equipment to free a man from his car by removing the roof.
The road has been fully reopened.