Samuel Lawrence Allen, 31, had been given a local anaesthetic for an unsuccessful tooth extraction on the day he was due to drive his Scania V8 lorry to Middlesbrough.

Colleagues at his employer’s yard, Delta Salvage in Sandtoft, near Doncaster, observed that he did not seem fit to drive when he returned from his appointment, but he did not ask to take the rest of the day off or remain on yard duties instead of taking the vehicle out on October 11 last year.

He crashed on the M62 near Selby less than half an hour after he had left Delta, and other drivers said they did not observe any attempt to brake before the transporter veered off the slow lane and struck the parapet.

Mr Allen, who lived in Epworth, near Doncaster, was trapped in the lorry’s cab and appeared conscious, but his condition had deteriorated by the time paramedics reached him. He went into cardiac arrest and died soon after.

A postmortem found no drugs or alcohol in his system and traces of the dental anaesthetic at only low levels. A fracture to his pelvis on impact led to his liver being lacerated and he died from a haemorrhage.

The inquest at North Yorkshire Coroner’s Court heard that Mr Allen, whose parents and siblings were present at the hearing, grew up in Norfolk and was a keen rower and a ball-boy for Norwich City FC. He loved driving large vehicles, and his job for Delta took him all over Europe hauling heavy loads. He had been planning to buy a smallholding with his partner, Scottish showjumper Claire Esler, and had put his house on the market shortly before he died.

Miss Esler said that although Mr Allen 'liked to live life at 100mph’ she felt he did not have a good enough work-life balance. He had been in pain with toothache for several months before his death, and she was not expecting him to drive or return to work after the appointment he had booked in Scunthorpe on the 11th.

When they spoke after the dental work, she said her partner ‘sounded terrible’ and said he was going back to the yard, but would stay there for the rest of the day rather than drive.

Evidence was heard from both the dentist and the dental nurse, who confirmed that the extraction of Mr Allen’s molar was aborted after around half an hour and he was advised to accept a further referral for surgical removal of the tooth in hospital. He ‘felt well’ on discharge and he was not told to avoid driving for the rest of the day, only to avoid strenuous exercise.

He also told the nurse that he was planning to go home and sleep after the consultation, although she did not think he seemed tired.

Delta Salvage’s director, Garry Hirst, said that the Scania was allocated only to Mr Allen and that he could arrange his load collections himself. The day before the collision, he had completed a run from Scotland to Northern Ireland after visiting Miss Esler at her home in Glasgow, catching a ferry from Cairnryan to Larne. On the 11th, he arrived back at the yard just after 9am. Mr Hirst was aware of Mr Allen’s tooth problems, but said that the appointment had been arranged around work and he had not requested the day off.

They chatted when Mr Allen returned to the yard at 12.30pm, and the driver seemed his ‘normal self’. Mr Hirst asked him if he was up for driving and said that he could go home, but Mr Allen responded that he was fine though his mouth was still numb. He departed the yard at around 2pm.

Another employee, Luke Blandy, said Mr Allen looked ‘drowsy’ and did not seem himself, and told him to go into the office and say he was not fit to drive.

The collision occurred on the westbound M62 between junctions 33 and 34 near Eggborough, at the Beal Lane footbridge over the motorway. Paramedics described how members of the public cleared trees and branches from the embankment to try and cut a path to the lorry’s cab door to enable Mr Allen to be freed.

A doctor who treated Mr Allen said it was ‘highly unlikely’ that the anaesthetic had had a role to play in the cause of the accident, but believed it probable that he had suffered an acute medical event.

Forensic collision investigator PC Patrick Green said that other drivers had witnessed the Scania veering off the carriageway between a gap in the barriers, clipping the edge of one, before travelling up the banking. They saw no signs of braking or slowing down.

The lorry’s tachograph and cameras were recovered, and had recorded a constant speed of around 54mph before the vehicle drifted off with no sign of driver input. There were no infringements of driver working hours on the tachograph.

The 19-metre gap in the barriers was to allow access to a farm track, but PC Green concluded that the lorry’s size meant their presence was unlikely to have made any difference to the outcome.

Although the camber of the road did take the lorry on a path towards the embankment, this was necessary to allow for drainage of the road and was not found to be defective.

PC Green’s investigation concluded that it was possible Mr Allen’s rest had been affected by the tooth pain, and that 2-4pm is a ‘peak’ time for sleep-related collisions. The ‘monotonous’ driving conditions even 20 minutes into his journey could have allowed him to drift into a series of micro-sleeps.

Recording a conclusion of death in a road traffic accident, area coroner Catherine Cundy said that she accepted Mr Allen may have ‘drifted into micro-sleep’ as a result of accumulated tiredness.

Yorkshire lorry driver, 31, died in M62 bridge collision when he fell asleep at the wheel after having dental treatment