UPDATE: The M25 has now reopened both anti-clockwise and clockwise after emergency services had shut the road between J17 and J18.
Delays around the areas of Chorleywood, Watford, Abbots Langley and surrounding areas are expected.
The M25 shut between J17 and J18 anti-clockwise after a collision involving a motorcyclist and a lorry required an air ambulance this morning (May 15).
Herts Police were called at 6.56am to reports of a collision. Both sides of the motorway were closed to allow the air ambulance to land.
One person has been arrested on suspicion of dangerous driving and police still remain at the scene.
Delays are expected leading up to the crash (anti-clockwise) and around Chorleywood and surrounding areas.
Police recommend to avoid the area.
Updates to follow.