SEVEN people including a Newport couple died in a massive motorway pile-up when they were engulfed by a thick smog caused by the smoke from a firework display, a court heard today.

The smog was so thick and dense that motorists likened it to having a tin of paint thrown over their windscreens.

Prosecutors, opening their case in a trial of a fireworks contractor, say that motorists on the northbound carriageway of the M5 near Taunton in Somerset had "no chance" as they drove along at around 8.20pm on the evening of November 4, 2011.

Retired Newport couple Anthony and Pamela Adams were among the seven people that died and 51 injured, including some seriously, in the pile-up.

A total of 34 vehicles, including cars and lorries, were involved in the crash on the motorway when they were driven into a thick smog, which had blown across the northbound carriageway from the firework display at the nearby Taunton Rugby Club.

Prosecutors allege that Geoffrey Counsell, who was the contractor in charge of the display, breached health and safety rules by failing to ensure the safety of others.

Counsell, 51, from Ashill, Somerset faces a charge of failing to ensure the safety of others contrary to the Health and Safety at Work Act. He denies the allegation.

Bristol Crown Court heard how Counsell, who ran Firestorm Pyrotechnics, set off 1,500 shots in just 15 minutes - just 200 metres from the motorway.

Peter Blair QC, prosecuting, told the jury: "The prosecution will be asserting that he (Counsell) had serious weaknesses in his planning.

"Essentially the prosecution say they experienced a loss of visibility, generated, we say, by a plume of smoke created by Mr Counsell from his firework display which had built up.

"It was dispersed because of the lack of wind mixed with the humid air and drifted in the direction of the motorway."

Mr Blair said a number of vehicles passed safely through the early stages of the smog - with some drivers later recalling the smell of firework smoke.

"The next group were less fortunate. They were in the vehicles that ended up in a multi-vehicle pile-up.

"Fifty one injured, some severely, seven people died. The prosecution say this was no ordinary patch of fog that just happened to be there that evening.

"Many of the descriptions they gave of the atmosphere were remarkable and distinctive. Some of them spoke of it as being as if someone had tipped a tin of paint over their windscreen.

"Their headlights had no effect whatsoever on penetrating what was in front of them. It was impossible to see what was ahead of them and the inevitable consequence was the multiple pile up."

The trial before Mr Justice Simon is expected to last up to six weeks.

Proceeding.