A police incident on the M1 in Hertfordshire that led to the M25 also being closed has caused widespread disruption for morning commuters.
Hertfordshire Police said it shut the M1 northbound, between junctions 6 and 6A, at about 05:15 BST, with a subsequent closure also being put in place on the M25 around junction 21A.
Traffic was temporarily diverted on to the A405 North Orbital Road and other surrounding routes.
Police said on X at 06:45 that the roads had been reopened but delays remained in the area.