A police officer died on New Year's Day while driving home to see his pregnant partner, an inquest heard.
PC Tokunbo Ezobi, 25, was travelling at more than 80mph when the accident happened on the A23.
His green Peugeot 406 collided with the central barrier on the Bolney flyover just after 3am on January 1 this year.
Mr Ezobi, known as Tok, had a young family and had been working in Brixton after transferring from Sussex Police to the Metropolitan force in September last year.
He was en route to Hove to see his pregnant partner Wendy Rudwick, their son Kane - who was one on Christmas Day - and Wendy's two other sons, Gareth, nine, and Reece, six.
After crashing, his car careered along the safety fence until it hit a lamppost.
It then veered into the opposite lane of the A23, ending up on its roof.
PC Michael Skingle, of Sussex Police, told an inquest in Haywards Heath yesterday fatigue may have played a part in the crash but the cause remained a mystery.
He said: "Mr Ezobi lost control of his vehicle. The reason for the loss of control is unknown."
Dr Gemma Stockford, a consultant pathologist at the Princess Royal Hospital in Haywards Heath, said Mr Ezobi died of a head injury.
Although there were no signs of a fractured skull, she said it was highly likely he had died instantly at the point of impact.
One factor in the crash concerned the central reservation barrier. According to PC Skingle, it should have deflected the vehicle.
He said it was possible the ground conditions had affected the posts holding up the barrier.
He said: "We can't say what would have happened if the barrier had pushed him away."
Coroner Roger Stone said the barrier had "played some part in the end result" but said there had also been an element of driver input.
He said: "What part has the barrier played in the death of Mr Ezobi? I can't be sure."
Mr Stone said it was "pure speculation" another vehicle could have distracted Mr Ezobi and recorded a verdict of accidental death.
He said: "Something unforeseen has happened in the otherwise normal course of events.
"There may be a crumb of comfort for the family in that Mr Ezobi would have had an instantaneous death and not have suffered.
"To the family and his partner I give my sincere condolences.
"I do hope in time they will be able to understand the evidence given and come to terms with his death. I hope they will remember him with love and affection."
Wendy Ezobi - who changed her surname from Rudwick by deed poll after her partner's death - declined to comment after the hearing.
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