The country's busiest road will close for the first time in its history with huge tailbacks predicted.
National Highways is blocking the M25 for a whole weekend to make way for demolition works in one of the largest infrastructure projects since it opened in 1986.
Motorists have been told to drive only if their journey is "absolutely necessary" as the unprecedented closure forces eight lanes worth of traffic through villages away from the motorway, with travellers to Gatwick Airport and the channel ports at risk of being impacted.
National Highways project lead Jonathan Wade said: “This is the first of five full closures of one of the busiest junctions on our road network.
“We have spent months planning for these closures and making sure there are diversion routes in place, but there will still be heavy congestion and delays."
It will shut in both directions between junctions 10 and 11 from 9pm on Friday, March 15, to 6am on Monday, March 18, to demolish the Clearmount bridleway bridge and install a large gantry.
The carriageway between junctions 9 and 11 carries between 4,000 and 6,000 vehicles per hour in each direction between 10am and 9pm on a weekend - and is just west of the M23's junction 7.
Jonathan added: “These improvements will bring long-term benefits to drivers who pass through this stretch of the M25, not to mention pedestrians, cyclists and horse riders who will also see positive changes in the area."
The diversion route will take drivers through Byfleet and Ottershaw - although drivers can also take the M25 in the opposite direction, around London, to reach their destination.
Junction 10 to Junction 11: Northbound A3 to Painshill Junction, A245 towards Woking, and then A320 to M25 Junction 11.
Junction 11 to Junction 10: A320 south towards Woking, A245 towards Byfleet and Painshill junction, Southbound A3 to Junction 10.
The road will close four more times between now and September 2024 to improve journey safety and reduce pollution as part of a £317m scheme of works.
Engineers say the project could not be completed without closing the road in both directions - and the works have been timed to avoid clashing with any major events.
The next full closure of the M25 is due to take place in April to allow for the installation of the new Clearmount bridleway bridge. Dates are subject to change.
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