The royal appeared concerned as his bodyguards treated the driver, who was reportedly unconscious and had to be cut free from his car by firemen – and the rider, who was thrown from his bike.
Prince Harry - pictured with Prince Charles - is "relieved" that both men involved in the accident are in a stable condition
One witness told the Mail that Harry's Range Rover took immediate evasive action. The driver, apparently fearing a terrorist attack, expertly steered the car through the damaged vehicles at high speed before coming to a stop further down the road.
The bystander said that he saw the Prince sat in the back with his head in his hands, constantly looking back towards the injured men.
Harry was insistent that they stopped, but on security advice he was then driven on. Other officers did attend the accident.
The police outrider has since been released from hospital, while the driver is said to be in a stable condition.
A spokesman for Prince Harry said on Thursday night: "The Prince was obviously very concerned and wanted to make sure both men were ok. He is relieved to hear they are both in a stable condition."