Kent Police are advising drivers to avoid the M20 between junctions 3 and 1 on the London-bound carriageway after a serious accident.
Police were called at 5.10am to a report that a lorry had jack-knifed and collided with the near-side barrier before falling down an embankment.
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The expansion of the probe came as Jeremy Corbyn declared Carillion's demise a "watershed moment" that should end "rip-off privatisation".
Tuesday afternoon's weather for the west of the region
Tuesday afternoon's weather for the east of the region