A driver suffered a cardiac arrest at the scene of a serious crash this morning along the A406.
The man, reported to be in his 20s, was rushed to St Bartholomew's Hospital in the City of London.
Emergency services, including London Fire Brigade, were called to the North Circular by junction 4 for the M11 and the Redbridge flyover at 7.47am.
London's Air Ambulance (LAA) was also called and was seen hovering above the crash, but did not land, London's Ambulance Service (LAS) has said.
The accident involving two lorries and three cars closed all four lanes southbound for around an hour.
A spokeswoman for LAS, said: "We sent a number of resources to the scene including two ambulance crews, our hazardous area response team, an advanced paramedic, a duty officer and a responder by car.
"We treated a man reported to be in his twenties for a cardiac arrest.
"He was taken as a priority to St Bartholomew's Hospital."
Police have not revealed any further details other than saying the driver is in a "serious" condition.
The cars and lorries have still not been recovered and three lanes remain closed.
Traffic on the M11 is queuing for five miles between junction 6 for the M25 and junction 4 at Woodford.
On the A406, there are long delays reported on Southend Road to Waterworks Roundabout.
A road traffic accident investigator stands beside one of the badly damaged lorries
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