Police were called at 6.08am on Thursday, 12 August to reports of a collision involving a cyclist and a lorry at the junctions of Primrose Hill Road and Adelaide Road.
Officers attended along with London Ambulance Service. The cyclist, a man in his 60s, was taken to hospital where he remains in a life-threatening condition. His next of kin are aware.
The driver of the lorry stopped at the scene and is helping police with their enquiries.
Detectives from the Serious Collision Investigation Unit are carrying out enquiries into the circumstances of the incident and would like to hear from anyone who was in the area at the time.
If you can help, please call the team on 020 8246 9820. Alternatively, call 101 or tweet @MetCC quoting CAD 1170/12Aug.