According to National Highways, the closure will run from 8pm on Monday 15 December until 6am on Tuesday 16 December 2025, following a request from the Kent & Medway Resilience Forum. The measure is being introduced in response to expected high passenger numbers at the Port of Dover and Eurotunnel in the run-up to Christmas.
To allow the contraflow to be installed safely:
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the London-bound M20 will be closed between junction 9 (Ashford) and junction 8 (Maidstone)
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the coastbound M20 will be closed between junction 7 and junction 9
National Highways says fully signed diversion routes will be in place during the overnight closure. Drivers are advised to follow road signs rather than SatNav instructions.
What happens when the motorway reopens
Once the M20 reopens on Tuesday morning, the Operation Brock contraflow will be active on a 13-mile stretch of the motorway between junctions 8 and 9.
Under the system:
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All HGVs travelling to the Port of Dover or Eurotunnel must use the signed Operation Brock routes and join the system at M20 junction 8
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Other coastbound traffic, including local freight and car drivers heading for the continent, will be directed to cross over into the contraflow on the London-bound carriageway
Drivers are required to follow all signage once the barriers are in place.
Enforcement and fines
Government guidance from the Department for Transport and National Highways confirms that enforcement officers will be deployed when Operation Brock is in force to intercept vehicles attempting to use alternative routes.
HGV drivers who fail to follow the signed routes risk being turned around and fined £300.
The authorities say signs, diversions and speed restrictions will be used to help drivers reach designated holding areas and manage traffic safely.
Decisions on when to activate different phases of Operation Brock are taken by Kent Police, depending on the scale of disruption to cross-Channel services.
Why Operation Brock is being deployed
Operation Brock is part of a wider set of measures designed to keep traffic moving through Kent and reduce the impact of cross-Channel disruption on local roads.
National Highways says the system is being deployed ahead of the Christmas holiday period to improve resilience during peak travel days.
