DEVELOPING STORY: M25 South Mimms congestion is building this Monday morning after a problem developed on the roundabout at South Mimms. The picture is still emerging and this article will be updated as more information comes in.
Drivers on the M25 in Hertfordshire are facing a miserable start to the week after a problem developed on the roundabout at South Mimms this morning, triggering major congestion on the motorway.
The trouble came to light shortly after 9am, when reports began to emerge of an issue affecting the roundabout at the South Mimms junction. Traffic on the surrounding stretches of London’s orbital motorway began to tail back quickly, and motorists caught up in it were soon describing heavy queues building in the area.
South Mimms sits on one of the most intensively used sections of the M25, where the motorway meets the A1(M) corridor and traffic heading for the capital, the Midlands and the North all funnels through the same junction. It is exactly the sort of spot where a localised problem can have an outsized effect — with so many vehicles passing through, delays can ripple for miles in both directions within minutes.
By the middle of the Monday morning rush hour, congestion around the junction was being described as major. Drivers heading through the area were being urged to allow far more time than usual — or to rethink their route altogether.
Key facts at a glance
- Where: the roundabout at South Mimms, on the M25 in Hertfordshire
- When: the problem was first reported on Monday morning, with live coverage beginning at around 9.15am
- Impact: major congestion and heavy queues on the surrounding stretches of the M25
- Advice: allow plenty of extra time, check live travel information before setting off, and follow any signs or instructions at the scene
How the morning has unfolded
9.15am: live coverage of the incident begins, with the first reports of a “problem” on the South Mimms roundabout and heavy traffic starting to build on the approaches.
Rush hour: as commuter volumes peak, the queues lengthen, with congestion around the junction described as major.
Now: the situation remains live. We are monitoring for further updates on what caused the problem and how long the delays are expected to last.
Advice for drivers
If your journey takes you anywhere near South Mimms today, the golden rule is to check before you travel. National Highways publishes live travel information for the motorway network, and a quick check before setting off could save you a long and frustrating crawl.
Those with any flexibility may want to delay their departure until the worst of the rush has passed. For shorter local journeys, surrounding A-roads such as the A1(M), A414 and A111 can sometimes offer an alternative way around the trouble — but expect them to be busier than usual as traffic diverts, and always follow official diversion signs rather than threading through residential streets on a sat-nav’s say-so.
And the usual motorway hold-up rules apply: keep your fuel or charge topped up, leave a safe gap in stop-start traffic, and never use the hard shoulder unless you are directed to do so.
A familiar trouble spot
This corner of the M25 has an unhappy habit of grinding to a halt. Only yesterday, the motorway was shut anticlockwise near Potters Bar after a vehicle fire, causing misery for drivers on almost exactly the same stretch.
If you do end up crawling past the service areas, you might at least pass the time with our rundown of how drivers rated every M25 service station — handy to know which stops are actually worth pulling into.
And for the trivia-minded stuck in the queue, here is one to mull over: you have never actually driven a full lap of the M25 — the road technically becomes the A282 at the Dartford Crossing.
We will keep updating this article as the situation develops.
