Emergency services were called on Thursday afternoon (7th January) just after 12.30pm to reports of a serious collision involving a van and a car on the A26 Eridge Road, just north of Crowborough.
The 35-year-old Kent man driving the car, a silver Seat Toledo, was flown by air ambulance to Kings College Hospital, London, with serious injuries.
The 51-year-old Kent man driving the van, a yellow Iveco Daily towing a trailer, was unhurt.
The road was closed in both directions into the evening for recovery and investigation work. Drivers are thanked for their patience and for following the diversions.
Anyone who saw what happened or who saw either vehicle just beforehand, or who has any dashcam footage which might assist, is asked to contact Sussex Police online or email email@example.com. You can also call 101 and quote Operation Smallfield.
Updated: Friday 8th January.