WITNESSES to one of the worst British motorway pile-ups - which claimed the lives of a Newport couple - described smelling gunpowder and seeing a wall of thick fog moments before the fatal crash, an inquest heard today.

Other motorists told how they hit "emulsion" and a "white curtain" as they drove along the M5 near Taunton on November 4 2011.

Seven people died and 51 were injured in the crash, which happened close to Junction 25 of the motorway.

A series of horrific collisions, which involved 34 vehicles, occurred on the south bound carriageway at 8.20pm - minutes after a £3,000 fireworks display concluded just 200ft away at Taunton rugby club.

Grandparents Anthony, 73, and Pamela Adams, 70, from Allt-yr-Yn; father and daughter Michael, 67, and Maggie Barton, 30, from Windsor, Berkshire; battle re-enactor Malcolm Beacham, 46, from Woolavington, Somerset; and lorry drivers Terry Brice, 55, from South Gloucestershire, and Kye Thomas, 38, from Cornwall all died and 51 people were injured, including some seriously.

West Somerset coroner Michael Rose resumed the hearing at Shire Hall, Taunton following the trial last year of firework contractor Geoffrey Counsell.

Mr Counsell, 51, who had been operating a display at the rugby club, was cleared at Bristol Crown Court of breaching health and safety laws on the night of the accident.

Lorry driver John Krostovnikoff told the inquest he was heading to Staffordshire from Exeter when he suddenly hit a wall of thick fog just after 7pm in the Taunton area.

"My visibility was clear and suddenly I was driving through... like a wall, then two seconds later I was through it," he said.

Luke Allen, who works as a handyman for Avon and Somerset Police, joined the northbound carriageway of the motorway at Junction 25 about an hour before the crash.

"As I joined the motorway it was fine. Not far from joining the motorway there was a wall of mist or fog right in front of me," he told the inquest.

"It was a like a white blanket... a curtain. It was like a white curtain in front of you appearing to be right across the carriageway.

"It was a dense white substance and I slowed down by decelerating. It took three to five seconds to pass through."

Sainsbury's deliver driver Ian Thorne was returning to his depot in Taunton when he hit a wall of thick smoke 200 yards long just a few minutes before the fatal crash.

He said: "I could see fireworks and then I could see the smoke they were giving off and I could see it was going to the direction of the motorway.

"It was white but I could see through it but I could also see it was 200 yards thick. It smelt of gunpowder."

Andrew Bibbings, an off-duty Avon and Somerset Police officer, was returning home to Portishead from Plymouth when he drove past Taunton at around 8.15pm

"I encountered a block of what I considered to be smoke. It was very slowly drifting from the left hand side of the northbound carriageway to the southbound side," he told the inquest.

"It took me two seconds to get through it. The density of the smoke remained constant and I formed the opinion the display was reaching a climax because of the amount of fireworks going off.

"I recognised what it was and it didn't cause me any alarm."

Mr Bibbings said his car headlamps did not penetrate the smoke, which he said smelled of sulphur.

"There is quite a difference between fog and what I consider to be smoke," he said.

"There was a large amount of fireworks going off and that led me to believe it was smoke from the firework shells."

Post mortem examinations found that pathologists were unable to ascertain causes of deaths for Mr and Mrs Adams and Mr Thomas due to fire damage, the inquest was told.

Mr Barton and his daughter died from multiple injuries, Mr Beacham suffered head injuries and Mr Brice succumbed to burns and inhalation injuries.