Four people were left injured after two cars crashed in Cublington on Sunday.
The vintage open top car and a green VW polo crashed at 12.02pm in Whitchurch Road.
All four people in the open top car were thrown from it after it tipped on its side.
The driver of the classic car a 69-year-old man suffered facial injuries. A female front seat passenger, 65, suffered shoulder injuries. Both were taken to Stoke Mandeville Hospital.
One rear seat passenger, a 69-year-old man suffered serious head injuries and was taken by Thames Valley and Chiltern Air Ambulance to Milton Keynes General Hospital. He has been transferred to the John Radcliffe Hospital where he is being treated and remains in stable condition.
A further rear seat passenger, a 63-year-old woman suffered injuries to her neck, elbow and ribs. She is being treated at Milton Keynes General Hospital.
The driver of the VW Polo a 26-year-old woman suffered minor bruising and shock. She was treated at the scene but not taken to hospital.
The classic car was part of a vintage rally that was taking place at Horwood House.
South Central Ambulance sent four double manned vehicles and were assisted by Bucks Fire Service. The police said the road had to be closed for several hours.
The cause of the collision is being investigated by the Roads Policing Unit at Milton Keynes. The officer in the case is PC Phil McGlue. Anyone with information or who witnessed the collision should contact him on non-emergency number 101