Police were called at 10.26pm on Thursday, 30 July to reports of a collision at Station Approach, Chislehurst.
Officers and London Ambulance Service [LAS] attended. At the scene a 44-year-old cyclist had fallen from his bicycle sustaining a head injury.
The cyclist was taken by LAS to a south London hospital where his condition is critical. Police await further updates.
Road closures and cordons were implemented. These were lifted at 3.15am on Friday, 31 July.
At this stage no other vehicles are thought to have been involved.