Hoy tested the track on Sunday but it was deemed too dangerous
The "man v machine" race between Chris Hoy and Lewis Hamilton at Wembley has been cancelled because of safety fears.
Triple Olympic cycling gold medallist Hoy and F1 champion Hamilton were due to face each other on day two of the Race of Champions event.
But Saturday's heavy rain combined with oil spills made the temporary track inside Wembley Stadium too slippery.
"The organisers have done their best, but you have to put safety first," said Scotland's Hoy.
"It's a huge disappointment as I was really looking forward to it and I know Lewis was too."
Hamilton was to race in McLaren's new road car against Hoy on an adapted version of the track bike he used to win his three golds in Beijing.
Instead, Hamilton took Hoy on a parade lap, and both men were cheered to the rafters by a 40,000 crowd.