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There were delays on the M20 after a fifth crash on the same stretch of motorway this week.
A car towing a trailer jack-knifed between J8 and J9 for Ashford in the coast-bound carriageway, just after the turn-off for Leeds just after 1.30pm.
Andy Ruffell had been driving home from a shopping trip in Aylesford with his two-year-old son in the car when he saw the accident.
The 28-year-old managing director said: "The silver estate car went to overtake a lorry and the trailer swayed one way and the car swayed the other so that it was fish-tailing in the middle lane.
"Then it jack-knifed into the central reservation. It seemed to happen in slow motion.
"We were about 60 yards behind but managed to stop and checked the driver was ok.
"The whole of the front of the car was destroyed."
Shortly before 2.40pm Kent Highways reported that a lane was blocked in the London-bound carriageway due to debris in the road.
Drivers were warned to leave extra time for their journeys.