A "serious" crash on the M25 this morning involving a motorcyclist shut the anticlockwise carriageway and caused 90-minute delays.

The collision at around 7.45am near junction 20, for the A41, caused gridlock traffic tailing back to near junction 22 for London Colney.

Watford Observer: Gridlock traffic near junction 20 of the M25 this morning.Gridlock traffic near junction 20 of the M25 this morning. (Image: National Highways)

Herts Police and the East of England Ambulance Service were called to the scene alongside National Highways officers.

There were seven miles of congestion with traffic being diverted via exit and entry slip roads near junction 20.

National Highways described the crash as "serious" and urged motorists to plan ahead and consider alternative routes if possible.

Watford Observer: Heavy traffic tailing back towards London Colney.Heavy traffic tailing back towards London Colney. (Image: Google Maps)

However, a Herts Police spokesperson said the motorcyclist was taken to hospital "as a precaution" after a collision with another vehicle on the motorway.

Officers were called at 7.45am and traffic was moving again by 8.45am, they added, although residual delays may be present.

National Highways tweeted at 9.20am that the stretch had reopened but there were still 45-minute delays. 

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