Motorists are advised to avoid the M25 anti-clockwise between junction 25 and 24 following an incident involving a vehicle transporter earlier this morning.
Road users are being advised to seek alternative routes.
The anti-clockwise carriageway is expected to remain closed for some time while emergency services deal with the incident, and for any necessary repairs to the road to be carried out.
Junction 24 is the exit for Potters Bar, while Junction 25 serves Enfield and Cheshunt.
Highways England traffic officers are working with the emergency services to manage the incident and get traffic moving as quickly as possible.