An ex-Formula 1 engineer dived in front of a lorry on the M20 days after changing his life insurance policies, an inquest heard.

But despite chilling evidence from the lorry driver and police that suggested former Ferrari chief mechanic Nigel Stepney committed suicide, a coroner said she could not be certain he had intended to take his own life.

Father of four, 56-year-old Mr Stepney was driving home to Colchester, Essex, from Belgium on Friday, May 2 when he pulled his silver VW van onto the hard shoulder between junctions 10 and 9 for Ashford, switched the lights off, got out and locked the doors.

Dutch lorry driver Jan Byl was travelling along the same stretch of motorway at about 1.30am, en route to Detling Aerodrome Estate near Maidstone, when he saw Mr Stepney’s van.

In a statement Mr Byl, who has been driving HGVs for 30 years, described how he started to move into the next lane to “give the van some room” and suddenly spotted Mr Stepney.

He said: “All of a sudden I saw the figure of a person dive out from the left. His arm was stretched out above his head. It was almost as if he’d been crouching down in front of the van and thrown himself into the path of my vehicle.

“Then I was on my CB radio and I shouted to my colleague, who was following behind: ‘Someone is diving in front of my truck - go right!’ I stopped and phoned the police. I didn’t want to go back and look – I was scared.

“I couldn’t have done anything about hitting the person. There was no time to brake or even think.”

PC David Kirk confirmed Mr Byl was driving within the speed limit - 56mph - and said damage to the front of the lorry showed Mr Stepney was “not standing upright” when he was hit and was “moving from left to right”.

Mr Stepney’s partner of nine years, Ash Naidoo told the inquest her boyfriend was not suicidal and had probably stopped on the busy road for a rest.

She said: “He drives great distances every day and he gets very tired. The onset is very sudden and he often has to pull over to have a breather.

“I believe he stopped for that reason. He was very fierce of character. He endured many things that could have persuaded him to do this eight years ago and he got through them. He loved his life and he loved his daughter too much to abandon her.”

A friend of the couple, Karen Day told the inquest she had been asked by Mr Stepney to witness the signing of some documents.

However, when she met him the following morning she was “shocked” to find he actually wanted her to be the trustee to two life insurance policies.

Mrs Day signed the papers at 8.15am on Tuesday, April 29 - just three days before Mr Stepney died.

Pathologist Nicola Chaston told yesterday's hearing in Folkestone that Mr Stepney died from multiple injuries, including a fractured skull, but she was unable to take a blood sample so could not say whether he had been drinking alcohol.

Coroner Rachel Redman noted Sergeant Ian Watson, who headed up the investigation, had concluded it was a suicide but said she had found no reason for Mr Stepney to take his own life and recorded an open conclusion.

Mr Stepney leaves children Laura, Cassandra and Joshua from a previous relationship and seven-year-old daughter with Ms Naidoo, Sabine.

He enjoyed a lengthy Formula 1 career and helped guide Michael Schumacher to five world championships.

But he was sentenced to 20 months in prison for sabotage, industrial espionage and sporting fraud after leaking almost 800 pages of confidential Ferrari information to McLaren ahead of the 2007 season.

He did not serve the sentence but lost his job and never worked in F1 again.