The cyclist, a woman believed aged 30, was pronounced dead at the scene [in Dulwich].
Next of kin have been informed. A post-mortem examination will be scheduled in due course.
The 40-year-old driver of the HGV lorry, a white Mercedes, stopped at the scene.
He was subsequently arrested in connection with the collision and taken into custody at a south London police station.
More top news
Fighting for their right to misuse nitrous oxide, approximately 60 or 70 protesters inhaled 'laughing gas' amid concerns over a clampdown.
The pilot, from the Gnat private display team died after the display aircraft he was in crashed near the CarFest event in Cheshire.
The annual cycling festival in London was the biggest ever this year - with more than 25,000 taking part today.