A traffic collision between a lorry and a motorcyclist caused huge congestion in the A406 at Redbridge roundabout.
The northbound lane, near the junction with the M11, was closed for an hour to allow London Air Ambulance to land.
Police officers also attended at 8.33am.
The motorcyclist has been taken to an east London hospital with his injuries and is serious but stable.
Moosa Rawat wrote on the Recorder’s Facebook page: “Drove past just as it happened. Looked like someone was doing CPR on the motorcyclist. Hope he is OK.”
Another driver said: “It looked serious, as someone was on ground apparently having medical treatment.
“The air ambulance arrived quickly and the police stopped the southbound carriageway to allow it to land.”
There have been no arrests and enquiries continue.
All lanes are now open but expect severe delays when travelling through the area. The congestion northbound runs until Ilford flyover.
Did you see the incident? Call our news desk on 0208 477 3821 or email ralph.blackburn@archant.co.uk.
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