Two passengers travelling in a vintage car were seriously injured after crashing during an annual parade of vehicles dating back to the early 20th century.
Police said the 1902 Mercedes Benz was involved in a collision with three other cars at around 11.35am at Reigate Hill, Surrey.
It had been taking part in the London to Brighton Veteran Car Run, a yearly event which sees hundreds of old cars flood the roads.
One passenger was airlifted to hospital with serious injuries while three others were also taken for treatment for minor injuries, Surrey Police said.
A picture shared online showed the mangled wreckage of the vehicle, which appears to have flipped, on the bonnet of a silver Ford C-Max.
Two passengers from the Ford were also taken to hospital with minor injuries, according to police.
A Mercedes GLE and a Fiat Fourini were the other vehicles caught up in the crash.
Police are appealing for witnesses to the incident, asking anyone with information to ring 101 quoting incident number P17279402