Lorry driver Stewart Welden was forced to relive the moment he struck Mr Groom on the M11 at Wednesday’s hearing.

Mr Groom escaped his uncle, John Groom, at Debden Station at around 10.20pm. He stood in front of the truck driven by Mr Welden about half an hour later.

Mr Welden, a lorry driver of 17 years, was delivering for Marks & Spencer. He was driving at 52mph, the vehicle’s maximum speed.

He told the inquest, at St Pancras Coroners Court: “I had just passed Junction 5 [near Debden]. It was very quiet. The next minute, this person just stood in the carriageway. He appeared in my headlights.

“He was just stood with his arms stretched like a starfish.

“I swerved but clipped him. At first, I thought, has that just happened?’

“But my headlight had gone out, so something had happened. I stopped and called the emergency services.”

Paramedics found Mr Groom’s body lying face down on the hard shoulder. He was pronounced dead at 11.08pm.

A toxicology report later found that there was no alcohol in his system.

Coroner: ‘I cannot consider suicide’

Though coroner Mary Hassell adjourned her verdict for Thursday, she did rule out suicide as the cause of Mr Groom’s death.

After hearing all evidence across two days, she said at the end of Wednesday’s hearing: “There’s no doubt in my mind that Matt stood in front of the lorry and that he knew it was going to hit him.

“What I have heard of his state of mind is that he was psychotic. My conclusion is that when he stood in front of that lorry, he was psychotic.

“Someone can only take their own life while conscious of what they are doing. Standing in front of the lorry while suffering psychosis means I cannot consider suicide.”

Dr Neil Sheehan, who assessed Mr Groom at Whittington Hospital three hours before his death on June 15, had said: “There were snippets suggesting he may be delusional.

“He spoke about a project he had been working on and also a code. He was not willing to go further: ‘If you don’t know, I can’t tell you. Can you give me your security clearance?’

“He changed quite quickly and became much more expressive on the topic of conspiracy. He mentioned Al Qaeda, the Russians, and how he crashed the stock market. It was as if he thought we were interrogators.

“There were a couple of occasions, fleetingly, where he said he wanted to end his life. But there was no evidence of serious intent and obviously not at the forefront of his mind.”

Brother slammed table as video was shown

Dr Sheehan said there was no need to give chase after Mr Groom walked out of the room.

CCTV footage at Wednesday’s hearing showed him leaving the assessment, held by Dr Sheehan and mental health nurse Joyce Tanner, at around 8.23pm.

Dr Sheehan and Ms Tanner sat still in the room for around 20 seconds, before Mr Groom’s uncle, John Groom, walked in.

Only after another 30 seconds did Dr Sheehan leave the room.

As the footage was shown, Mr Groom’s brother, Joe Groom, angrily slammed his hands on the table he was sitting at.

But Dr Sheehan said: “I wouldn’t say he ‘stormed out’.

“At the time he left, there was nothing he had said that led me to believe he was in imminent danger, which is probably why I didn’t chase him immediately.

“It’s not particularly unusual in a psychological assessment for people to leave for a short period to gather their thoughts, or have a cigarette. I thought maybe he was going to get moral support from his uncle.”

Dr Sheehan found them at the A&E entrance, and tried to convince Mr Groom to return. He then bolted, chased by John. Less than three hours later, he died on the M11.

Asked by Mr Groom’s father, Tony Groom, if he thought of pursuing him, he responded: “I didn’t think I’d catch him. I have no training in control and restraint. I didn’t consider that safe for myself or Matt.”