What's happenning: The closure, which lasted several hours, was put in place after Essex Police were called at 10:25 BST on Wednesday.
Why it matters: The incident caused significant disruption for motorists, with delays of at least 40 minutes above normal travel time reported.
The key details:
Essex Police responded to reports of concerns for a woman's welfare
The woman was later placed in the care of ambulance services
National Highways diverted traffic via exit and entry slip roads during the closure
What they're saying: A spokesman for Essex Police said: "The closure was put in place after we were called to reports of concerns for the welfare of a woman at about 10:25. The woman is now in the care of the ambulance service."
The bottom line: While the A12 has reopened, residual delays may continue as traffic returns to normal. Motorists are advised to check their routes before travelling.
